About ten cents. Almost all of it goes to the chain, not to us.
No percentage is taken here. You pay Solana, plus a small relayer margin if you use one. Measured from the lamport deltas of a real deposit and withdrawal, not estimated:
| item | SOL | what it is |
|---|---|---|
| deposit transaction | 0.000005 | network fee |
| nullifier record | 0.001002 | permanent on-chain rent |
| withdrawal transaction | 0.000005 | network fee |
| relayer margin | 0.000015 | at the floor |
| per note | 0.001027 | — |
The nullifier record proves a note has been spent. It has to outlive the note permanently or the note becomes spendable again, so the chain charges rent for it once and for good. Nobody chose to levy it and no operator collects it.
The same ~0.001 SOL covers a 0.1 SOL mix and a 10 SOL mix — about 1% of the first and 0.01% of the second. If the fee bothers you, the answer is a larger denomination.
Waiting. It buys more privacy than any fee decision, and it is free. A withdrawal in the same few minutes as its deposit is paired on timing whatever the proof says.
See also the walkthrough and why an exchange is not a substitute.