Rollup cost models are usually presented as an execution story, but the durable tradeoff remains data availability. The question is not only whether users get cheaper transactions. It is whether the system remains legible when demand spikes, sequencers fail, or settlement assumptions are stressed.
The Constraint That Refuses To Disappear
Data availability is where optimistic projections meet operational reality. Teams can subsidize fees, compress calldata, or tune batching windows, but users still depend on the chain publishing enough information for independent verification.
That makes the economics less glamorous and more important. Sustainable rollup design is a balance between throughput, verification cost, and graceful failure modes.