Every Layer 2 advertises a low gas fee. None of them advertise the rest of the bill. If you move funds between rollups for a living, the headline fee is rarely the number that matters.

The four components of L2 cost

  1. Execution fee — what you pay the sequencer.
  2. Data availability cost — what the rollup pays to post your transaction to the base chain.
  3. Bridge fee — charged when you move value onto or off the rollup.
  4. Time cost — the delay before a withdrawal is final, which has a real price if your capital is working.

Execution fees have collapsed. The bridge and the waiting period have not.

Why fragmentation is the hidden tax

Liquidity is split across a growing set of rollups. A trade that would be deep on one venue may slip badly on another, and moving capital to chase the better price costs a bridge fee in both directions. For active users, the sum of these friction costs can exceed the gas saved.

A practical rule

Compare rollups on round-trip cost, not entry cost: bridge in, execute, bridge out. Include the withdrawal window. A chain with slightly higher gas but native liquidity often wins on total cost.

Layer 2Typical entry costWithdrawal window
Optimistic rollupVery lowHours to days
ZK rollupLowMinutes to hours
ValidiumVery lowNear-instant

The direction of travel is clear — fees keep falling and bridges keep improving. Until then, price the whole trip.