For equal base quantities filled symmetrically around an unchanged reference mid, define N as the mid-price notional of one side. Gross spread capture = N × spread / 10,000. Total maker fees = 2N × fee / 10,000; a negative fee is a rebate. Entered adverse-selection / markout cost = N × adverse bps / 10,000. Net = gross − fees − adverse cost. Break-even full spread = 2 × fee + adverse bps. This is round-trip unit economics conditional on both fills, not expected daily profit. Fill probability, queue priority, open inventory, funding, and hedge costs beyond the entered adverse cost are excluded. Fee defaults are examples, not any exchange's live fee tier.

Coinbase: maker fees and rebates