Amex's business model is called "Spend-Centric". Their transaction fees are larger than that of Visa and Mastercard so they make more money on each purchase of their consumers Amex Card. They encourage more consumers to use their card by giving rewards points back to them for using their card. Along with the annual fee of having their top 3 or 4 rewarding credit cards, they make a lot of money based off of that system.