The U.S. Supreme Court heard arguments this month on litigation concerning a New York state law that prohibits merchants from adding a surcharge to any payment made using a credit card. New York’s law is similar to prohibitions in other states, which collectively account for more than 50% of the U.S. population. In addition to bans against surcharges, most of those states also prohibit merchants from adding credit card processing fees they pay to the price of goods they sell. These states do permit merchants to offer discounts if people pay with cash instead of a credit card. A surcharge and...