Isometric keeps up to 5% of the premium a trader pays. The pool that backs the position keeps the rest, and that share is everything the protocol takes from a pool.

Your balance is never charged. There is no fee to deposit or withdraw, and no annual or performance fee on what your shares are worth.

When a premium cannot cover what the pool must set aside to back a position, the protocol refuses the trade rather than open it at your expense. The protocol's share is paid out of what is left after that cost, which is why it is capped at 5% rather than fixed at it.

The 30d APY on the pool page is measured from share value, so it is what depositors earned after the protocol's share and after payouts to winning traders. How the yield works explains where the return comes from.

Each deposit and withdrawal is one Base transaction, plus a one-time approval for each asset, and costs a fraction of a cent in ETH from your wallet.

The protocol pays for settlement, price samples, and automatic payouts to traders from its operating budget. Neither pool ever pays for them.

The protocol's share is a parameter. Governance can raise it, but only to a ceiling fixed in the contract code, and a change takes effect after a 48-hour delay that is visible on chain the whole time. Protocol parameters explains how a change happens.