I guess I always assumed subway systems do enough volume that they get special deals with credit card companies. But for somebody who makes a niche API that does not necessarily have such a large captive customer base, couldn't they mostly get ripped off? I haven't yet used one of the subways where they let you use your cc as a ticket (or I'm just stodgy and always still buy the ticket at the machine).

You're point is fair, though. CCs are big enough that they will doubtless have many solutions to this. My statement was too strongly worded.