Customers have a veritable smorgasbord of purchase options. Interchange fees relate to credit card payments specifically, the third most common way Americans spent in 2016, according to the most recent statistics available from Blackhawk Network. Whenever a customer uses his or her credit card, the merchant processing the card also makes a payment, in the form of fees, which are sent to the bank or credit card network that issued the card. How much merchants pay in interchange fees varies, but generally speaking, the more expensive a purchase is, the higher the fees, along with a flat rate that comes with every credit card purchase. Debit cards may also include interchange fees.