Stripe charges 2.9% plus $0.30 per transaction. If you have an average transaction size of $100 you're paying $3.20 in fees (3.2%). There are several no annual fee credit cards that give the consumer 2% cash back. That leaves 1.2%. This 1.2% isn't pure profit. Things like fraud protection will cut into this. There are also several groups that need to split whatever is left of that 1.2%. Stripe needs to make money, Visa/MC need to make money, the bank offering the card needs to make money.