It looks like they are charging a flat fee to everyone regardless of how they pay. I think the CC companies tend to get mad if you charge a fee to people paying

It looks like they are charging a flat fee to everyone regardless of how they pay. I think the CC companies tend to get mad if you charge a fee to people paying credit at stores where paying by check or cash is an option. IIRC you can also get around it by having a cash "discount".