Credit card companies make a decent amount of their money from the interchange fees, but the majority of their income comes from interest, cash advance fees, and penalty fees, all of which the well-off credit card user paying off their balance each month does not contribute to. So credit card companies are probably making more money off their less-well-off users as a group than the more-well-off, though it may still be that individual well-off users are more profitable than other individuals.