I have a checking account with $100 in it. I go to a Starbucks and charge a $6 cup of coffee. I now have $94 in my checking account and Starbucks has $6. There is no fee for either. I don't care if that cup of coffee costs the bank a million fucking dollars. The customer doesn't pay and the business doesn't pay. That's all the public will see or care about. If that cup of coffee costs one penny more they will keep using their debit card. Remember I'm not talking about credit. Credit is another story and something Bitcoin isn't currently competing with on a large scale.

Edit: I'm talking about Pin Debit using qualified large merchants.