Chakravorti and Emmons model side payments in a competitive credit‐card market. If competitive retailers absorb the cost of accepting credit cards by charging a higher goods price to everyone, then someone must subsidize convenience users of credit cards to prevent them from defecting to merchants who do not accept cards. The side payment could be financed by card users who roll over balances and pay interest. It is rational for them to do so if their subjective discount rates are high enough. Charging different prices to different customers based on the underlying cost of the payment instrument would be more efficient for retailers. However, banks may offer incentives to attract convenience users because some of them may become interest‐paying users (“revolvers”) in the future.