Rollups vs Sidechains Throughput Cost Comparison for High-Volume Apps

A practical, number-driven guide to choosing between rollups and sidechains for apps pushing millions of transactions. We benchmark throughput ceilings, fee components, and real per‑million‑tx costs post‑EIP‑4844, and show how DA choices (Ethereum blobs vs Celestia vs AnyTrust) swing unit economics.

Who this is for

Decision‑makers at startups and enterprises planning high‑volume payments, social, gaming, or exchange workloads that cannot afford surprises in cost or capacity.

Executive summary

Post‑EIP‑4844, rollups using Ethereum blobs can hit triple‑digit TPS for complex actions and four‑digit TPS for simple transfers, with fees dominated by blob data costs; swapping the DA layer (e.g., to Celestia or AnyTrust) can cut L2 data costs by two orders of magnitude for data‑heavy workloads. (eips.ethereum.org)
Sidechains (e.g., BNB Smart Chain, Polygon PoS) deliver very low per‑tx fees and high observed throughput, but with different trust and security assumptions than Ethereum rollups; today’s average fees are in the cents-to-sub‑cent range and can be policy‑driven (e.g., BSC 0.05 gwei min gas). (bscscan.com)

1) The essential difference (only what matters for cost and TPS)

Rollups (Optimistic or ZK) execute off‑chain, then publish data for verification. Your fee consists of:
- L1 data cost (calldata before 4844; blob data after 4844).
- L2 execution gas.
- ZK rollups also pay proof generation/verification costs (amortized). (specs.optimism.io)
Sidechains run their own consensus and fee markets. You pay the chain’s gas fee only; there is no forced L1 data posting unless you architect it. Fees and capacity are governed by that chain’s parameters and validator economics. (bscscan.com)

Security trade-off in one line: rollups inherit Ethereum’s data availability and settlement guarantees (if using Ethereum DA), whereas sidechains add a bridging/trust layer and distinct validator set. For “validium/AnyTrust” designs, DA is delegated to a committee or external DA layer to cut costs at the price of extra trust assumptions. (docs.arbitrum.io)

2) Throughput headroom you can actually plan around

Think in gas-per-second, then translate to your tx’s gas profile.

OP Stack reference (Base): 32.5M gas/sec. That implies:
- ~1,548 simple transfers/sec (≈21k gas/tx).
- ~162 DEX swaps/sec (≈200k gas/tx). (docs.optimism.io)
Arbitrum (proposal under vote/rollout): raise gas target to 10M gas/sec. That implies:
- ~476 transfers/sec or ~50 swaps/sec at baseline target. (forum.arbitrum.foundation)

Observed sidechain throughput today (24h snapshot style, not maximums):

BNB Smart Chain: ~101.6 TPS over last 24h (with low average fees). (bscscan.com)
Polygon PoS: ~47.6 TPS over last 24h (fees typically ~one cent in recent quarters). (polygonscan.com)

What this means:

If you need 100+ complex swaps/sec, a Base‑style OP chain has the headroom out‑of‑the‑box. An Arbitrum chain can hit that with parameter changes or by splitting workloads. Sidechains can absorb large bursts but you share blockspace with the whole ecosystem. (docs.optimism.io)

3) Fee components after EIP‑4844 (Proto‑Danksharding) and why they matter

EIP‑4844 introduced ephemeral “blobs” with a separate fee market. Blobs are short‑lived (~18 days) and much cheaper per byte than calldata, drastically improving L2 economics. Target capacity starts at 3 blobs per block (max 6). (eips.ethereum.org)

Rollup fee = L2 execution gas + L1 data fee (now blob‑priced) + (for ZK) proving cost:

OP Stack: L1 data fee varies with Ethereum’s blob base fee; scalars are in SystemConfig after Ecotone. (specs.optimism.io)
Arbitrum: total fee = L2 gas price × (L2 gas + buffer for L1 data), with L1 price/byte estimated and compressed (Brotli). Fee splits include L1 base fee, L2 base fee, and surplus components. (docs.arbitrum.io)
ZK rollups: add proving costs; current estimates put proving around fractions of a cent per tx at scale (improving over time). (chorus.one)

Sidechains: a single L2‑style fee paid to validators; price depends on chain policy and gas demand. Today’s averages:

BNB Smart Chain: average tx fee ~ $0.03 (24h), with a network‑wide policy shift in Oct 2025 lowering the minimum gas price to 0.05 gwei (pushing many txs near half a cent). (bscscan.com)
Polygon PoS: Q1 2025 average ~ $0.01 per tx; many periods are lower. (messari.io)

4) Data availability choices swing your unit economics

You can combine Ethereum settlement with different DA backends:

Ethereum blobs (default, most secure): predictable logic, costs fluctuate with blob fee market. Stakeholder docs and dashboards show blob costs well below calldata and expected to rise/fall with demand. (eips.ethereum.org)
Modular DA (Celestia) via OP Stack or Orbit integrations: orders‑of‑magnitude cheaper DA for data‑heavy apps. OP Stack x Celestia and Arbitrum Orbit x Celestia are production‑grade options, including Ethereum fallback. (blog.celestia.org)
AnyTrust/validium‑style (e.g., Arbitrum Nova or custom Orbit): DA is provided by a committee; L1 sees only certificates, dramatically lowering on‑chain data costs. (docs.arbitrum.io)

Current reference points:

Example cost model (OP Stack): 1,000,000 ERC‑20‑like transactions at ~120 bytes each
- Posting to Ethereum (calldata/blobs): ~$78,558 per million tx.
- Posting to Celestia: ~$332 per million tx (≈99.6% cheaper). (docs.gelato.cloud)
Celestia DA pricing discussions indicate live prices at low cents per MB with proposals moving toward tiered volume pricing; the headline is that Celestia DA is often one to two orders cheaper than Ethereum blobs for sustained high throughput. (forum.celestia.org)

5) Practical, apples‑to‑apples cost examples

Below are planning numbers you can sanity‑check in due diligence. Swap in your own tx sizes and gas profiles.

A) Social app: 1,000,000 lightweight posts/day (~120–150 bytes/tx)

OP Stack rollup, Ethereum DA: ~$78.6k per million (DA component), plus small L2 execution fee. If your posts are 150 bytes, scale proportionally (~25% more). (docs.gelato.cloud)
OP Stack rollup, Celestia DA: ~$332 per million (DA component). Same execution layer as above. (docs.gelato.cloud)
Arbitrum AnyTrust (Nova‑style config): typically an order of magnitude cheaper than full rollup DA for data‑heavy apps, with a mild committee trust assumption. (docs.arbitrum.io)
Polygon PoS sidechain: ~ $10,000 per million at $0.01 average. (messari.io)
BNB Smart Chain sidechain: ~$30,000 per million at $0.03 average fee; policy shifts toward 0.05 gwei can push this toward ~$5,000 per million. (bscscan.com)

B) Exchange: sustained 100 swaps/sec (≈200k gas/tx)

OP Stack chain (Base‑like): 32.5M gas/sec comfortably supports ~162 swaps/sec headroom at L2; your limiting factor will be DA costs and priority‑fee bidding under load. (docs.optimism.io)
Arbitrum with 10M gas/sec target: ~50 swaps/sec; to reach 100, consider higher targets, workload partitioning, or a dedicated Orbit chain with tuned parameters. (forum.arbitrum.foundation)
Sidechains: observed BSC/Polygon TPS supports the workload, but you share space with network‑wide activity and trade Ethereum‑native settlement for bridge assumptions. (bscscan.com)

6) Finality and withdrawals: the hidden UX cost

Optimistic rollups: standard withdrawals to Ethereum wait ~7 days (challenge window). Fast‑withdrawal services/commit tees can shorten this with additional trust. If you’re bridging user balances frequently to L1, factor this delay into treasury and liquidity ops. (support.arbitrum.io)
ZK rollups: withdrawals finalize once proofs verify on L1—minutes to under an hour under typical conditions. Consult your target ZK stack’s current parameters. (docs.zksync.io)

7) Sidechain reality check (2025)

BNB Smart Chain: very low fees, high daily throughput, and aggressive fee‑floor policy moves (0.05 gwei) that can bring most simple txs near ~$0.005; average 24h fee recently ~ $0.03. Good for ultra‑low‑margin micro‑transactions if you accept BSC’s validator/security model. (bscscan.com)
Polygon PoS: mature ecosystem; Q1 2025 average fee around $0.01 per tx; observed daily TPS in tens rather than hundreds, but roadmap upgrades continue to raise limits. (messari.io)
Gnosis Chain: sub‑cent fees, lower observed TPS; often chosen for payments/utility use cases with Ethereum tooling. (chainspect.app)

Security footnote: bridge incidents historically dominated crypto losses in 2022; if your value depends on bridging between a sidechain and Ethereum, budget for heightened security, audits, and incident response. (chainalysis.com)

8) Emerging best practices that materially cut your costs

Pack blobs efficiently. Aim for high blob occupancy before posting (batching, Brotli, and intelligent timers). The blob market charges per blob unit; paying for half‑empty blobs wastes dollars at scale. (docs.arbitrum.io)
Choose DA per workload tier:
- Ethereum blobs for high‑value DeFi and when you need L1‑native guarantees.
- Celestia/EigenDA or AnyTrust for chatty, low‑value or social data to 10–100× your cost savings.
- Use Ethereum fallback if your modular DA is down. (blog.celestia.org)
Tune gas targets and floors:
- Arbitrum: raising gas target (e.g., 7M→10M gas/sec) increases capacity; set a minimum L2 base fee to deter spam and smooth volatility. (forum.arbitrum.foundation)
- OP Stack: adopt Flashblocks/Rollup Boost for sub‑second block times when UX requires it; ensure your DA/posting pipeline can keep up. (docs.optimism.io)
Understand priority fees. On busy L2s, a minority of addresses can account for most priority fee revenue; build fair‑ordering or auction strategies to avoid runaway bidding wars in your app. (coinlaw.io)
For ZK stacks, monitor proving costs. Hardware and prover upgrades trend down the per‑tx proof cost; re‑baseline quarterly. (chorus.one)

9) Decision guide: when rollup vs sidechain makes financial sense

Choose an Ethereum rollup (Ethereum DA) if:

You custody high‑value assets or rely on Ethereum‑native composability.
You can tolerate ~7‑day optimistic withdrawals (or choose a ZK rollup for faster exits).
Your DA budget with blobs pencils out versus sidechains. (eips.ethereum.org)

Choose an Ethereum rollup with modular DA (Celestia/EigenDA) or AnyTrust if:

Your app posts lots of small messages (social, gaming state, receipts).
You need Ethereum settlement with dramatically lower DA costs and accept a mild trust assumption for DA or an external DA layer. (blog.celestia.org)

Choose a sidechain if:

Your unit economics demand sub‑cent fees today, and your risk model accepts the sidechain’s validator/bridge assumptions.
You can mitigate bridge risk (e.g., custody on‑chain only temporarily; use exchanges/fiat on/off ramps to avoid hot bridges for end‑users). (bscscan.com)

10) Brief in‑depth notes on how to scope your own cost model

Profile your transactions:
- Measure average bytes per tx (post‑compression) and average L2 gas per tx.
- For swaps or mints, sample gas across peak periods.
Convert to blob/DA costs:
- With Ethereum blobs, estimate cost/MB at your target blob base fee; stress‑test with 2–5× spikes.
- With Celestia or AnyTrust, use provider quotes and incorporate quorum/retention needs. (forum.celestia.org)
Add execution and (if ZK) proving costs:
- Execution gas × L2 base fee + amortized proof cost. Keep a separate line for sequencer margin and priority fees under surge. (docs.optimism.io)
Simulate 3 loads:
- Quiet: 10% of peak.
- Nominal: median day.
- Surge: top 5% hour.

A single spreadsheet tab with these four lines (DA, execution, proving, priority) is usually enough to converge on the correct architecture in one workshop.

What 7Block Labs recommends in 2025

For consumer-scale chatty apps: OP Stack or Orbit with Celestia DA (Ethereum fallback enabled) to keep DA <$1k per million events while preserving Ethereum settlement. Start with one chain per product tier to cap priority fee contention. (blog.celestia.org)
For mid‑to‑high value DeFi: Ethereum DA first; plan a “DA switch” runbook (with governance guardrails) so you can temporarily fail over to Ethereum calldata/blobs during third‑party DA incidents. (chaincatcher.com)
For extreme cost sensitivity with limited on‑chain value: BNB Smart Chain or Polygon PoS are pragmatic; wrap bridge exposure with custodial or delayed‑settlement patterns. (bscscan.com)

Sources for the numbers referenced

EIP‑4844 blobs: capacity, pricing model, ~18‑day retention. (eips.ethereum.org)
OP Stack throughput and DA options; Flashblocks/Rollup Boost. (docs.optimism.io)
Arbitrum AnyTrust/DA model and fee breakdown; gas target proposal to 10M gas/sec. (docs.arbitrum.io)
Celestia DA pricing context; OP Stack integration; cost deltas at 1M tx scale. (forum.celestia.org)
Sidechain fee/throughput snapshots (BscScan, PolygonScan/Messari). (bscscan.com)
Optimistic withdrawal windows and fast‑withdrawal tradeoffs. (support.arbitrum.io)
Bridge risk background (context for sidechain decisions). (chainalysis.com)

If you want us to benchmark your exact workload (payload sizes, compression ratios, burstiness) against OP Stack/Orbit, Celestia/EigenDA, and the major sidechains—and hand you a one‑page total cost curve with migration triggers—reach out to 7Block Labs.