Surcharging
Adding a fee at checkout when the customer pays by card, so the cost of acceptance lands on whoever chose the card.
The logic is simple: if a premium credit card costs the merchant 2 percent and cash costs next to nothing, why should every customer split the bill? The card networks long disagreed and banned it in their merchant contracts through so-called no-surcharge rules. In the US those rules loosened after a 2013 settlement, and in Australia merchants may pass on their actual cost of acceptance.
The EU went the other way. Since PSD2 took effect in January 2018, surcharges are banned on consumer cards covered by the interchange cap, which in practice means almost every ordinary debit and credit card. What remains are mainly corporate cards and three-party networks like American Express. The argument was that once interchange had been regulated down, there was nothing left to pass on. Airlines have nonetheless shown great creativity in renaming the fee.