Comment by AdieuToLogic

> They're set at whatever the payment networks can get away with. There's nothing that says that's good for anyone else, although it is very good for Mastercard and Visa.

MasterCard and Visa are more like clearinghouses. The decision makers are their members having "access to the rails", issuers and processors, which are either banks, subsidiaries owned by banks, or companies sponsored by the aforementioned two (which very often includes one or more banks getting an ownership percentage).