Credit card interest rates average 23%, far exceeding rates on other major loan or bond types. To understand the drivers of these high rates and the economics of credit card banking, we analyze regulatory account-level data on 330 million monthly accounts, representing 90% of the US credit card market. While high default rates partially explain high card interest rates, netting these out still leaves an average interest spread of 10%. Non-interest expenses, including rewards, are more than offset by corresponding non-interest income. Operating costs are large, suggesting a significant role for market power, and explain a sizable part of rate spreads. Yet even after subtracting them, banks’ return on credit card lending is over four times their average return on assets. Using the cross section of accounts by default risk, we estimate a price of default risk. We find it is similar to that in high-yield bonds, and implies the average card borrower pays a 4.2% risk premium. Yet, there remains a substantial zero-beta rate of 3% that is unexplained by risk and is specific to credit card lending.