[RC30]

Most credit card companies require you to charge the same price cash or credit. If you as a credit customer see someone offer a discount for cash, you can call the credit card company and they will have a talk with the merhcant. Technically/contractually if they want to take credit cards they have to keep prices the same between cash & credit. Also (although I see this done quite a bit) I believe most credit card companies don’t like minimum charge amounts.

[Publius Valerius]

I believe most credit card companies don’t like minimum charge amounts.

That's true. Merchants cannot set minimum prices for credit card transactions without violating the terms of their agreement with the credit card company.

[Freedom4US]

It’s not a discount for cash, it’s a surcharge for using a credit card, which is perfectly reasonable in my view.