The difference is that Amazon makes a profit selling goods and uses those profits to pay the fees for credit card acceptance.  The merchant (Amazon) pays fees to the card companies so they can make payment methods easy to their customers.  They then sell more goods more efficiently and make more profits.  The cost of accepting various payment methods is “built-in” to their product prices and is really no different than Amazon providing free shipping when the customer spends a certain amount.  In our case, the bank is acting as the “merchant” and, as such, is collecting a convenience fee required to pay for costs associated with various card payments.  This channel has costs from the credit card companies and the convenience fee collected is used to help cover these costs.