15%? Try 1.5-6% and visa/mastercard and others get part of that. 6% would be considered very high risk. If you're paying more than that you're getting robbed. Casino's doing business in places where they shouldn't be might be paying that. But you see what happens there with recent events.
But there is good money in processing. One guy even made a movie about his high roller life with the money he made.
As the old saying goes. The easiest way to rob a bank is to own one.