>Visa's 2% fee may seem low but from a scale and competitive standpoint it is fairly absurd - they are making 80% gross margins on $30b of revenue to do what boils down to a few API calls and some fraud repayment.

The banks issuing Visa cards do fraud repayment. Visa gets paid for their network, and specifically their network of higher income spenders who want to play the rewards game. Also, note that Visa does not earn 2% of transaction totals. A signification portion of total card processing fees goes to the card issuing banks to pay for rewards and fraud repayment.