Earlier quoted context omitted.
Merchants are allowed to charge a surcharge for credit card usage in the US.
IIRC, even now they're still not allowed under the network rules. A cash discount IS allowed. So, a $.10/gal cash discount for gas is OK. The register having a sign that says "we charge $.75 for card transactions under $30" is not. Not that you don't see that all the time... (It's been a while since I've drank the regulatory alphabet soup on this, could be mistaken. )
https://www.creditcards.com/credit-card-news/what-are-my-rig...