The issue: Merchants pay a percentage of each charge to credit card companies. When American Express forms contracts with retailers, the credit card company prohibits retailers from expresa shoppers to hwen other cards that charge lower fees. For instance, merchants who accept Amex card payments can’t offer shoppers different prices depending on how they pay, even if the transaction fee is higher when they swipe an Amex. Retailers hate this because it’s expensive. According to the Brookings Institution»Use a typical Visa or Mastercard branded credit card and the merchant will probably pay fees ranging in the 2 to 3. It all adds up.