[Fat Charlie]

Credit cards aren't interest free loans, the interest is just hidden in fees that are themselves hidden. They make their money every time you use the card, and stores just roll that into the price of everything. Now that stores are allowed to have different prices for cash and credit, you get to see how interest free the card really is.

Luckily, most places don't do that, so card fees are rolled into your price even if you pay cash. That makes credit, especially rewards cards, a really good move. Regular cards give you convenience and some benefits in return for those fees you can't get out of paying even if you use cash, and rewards cards let you claw back some of it. Using credit means having a buffer that you don't have to pay for: I can get to my savings, but they're not the most liquid. I don't have a box of cash buried in my backyard- my kids have more cash in shoeboxes in their rooms than I have in my pocket. But I've got a ton of purchasing power in that pocket if I really need it.