Crypto venues typically charge options fees as a percentage of the underlying’s value, capped at a share of the option’s premium. The cap is the interesting part.
The problem it solves
Consider a far out-of-the-money option trading at a tiny fraction of spot. A fee computed on the underlying’s full value could easily exceed the entire premium — you would pay more to trade the option than the option costs.
Nobody would trade it. Those strikes would have no liquidity, no open interest, and would effectively not exist.
Capping the fee at a share of premium keeps them viable: cheap options carry cheap fees, so the wings of the book remain tradeable.
Why anyone reading structure should care
Because it is part of why the wings have any open interest at all — and the wings are where skew is measured, since skew is a comparison of out-of-the-money puts against out-of-the-money calls.
A fee structure that priced the wings out would leave skew unmeasurable, and a dealer map with nothing in the tails would understate how far the structure extends. A fee cap is not usually thought of as market structure; here it is.
What it does not solve
The cap makes the fee proportionate. It does not make the round trip cheap. On a very cheap option the spread is typically the dominant cost, often far larger in percentage terms than any fee — the same relationship as price impact against fees on-chain.
So a trader attracted to a far out-of-the-money option by its low absolute price is usually paying a very high percentage cost to get in and out, and the fee cap has protected them from only the smaller half of it.
The general rule
Cost is the round trip at your size, not the headline fee. That is true on a pool, on a perpetual and on an options chain, and it is the number that decides whether a trade with a real edge survives contact with the market.