Exactly this. What compounds it is when CVS offers a coupon for say 40% off of a regular priced item. The shelf won’t have a buy one get one sign on it, but the register sure as hell will bark and say you can’t use the coupon because it’s on sale.

But you don’t pay it off right away. You let that $200 roll over to the next month. The RedCard has an interest rate of 24.9%. You’ll have to pay $49.80 on in interest, bringing your grand total to $249.80. Even after the $10 you get back, you’ll pay $247.31. That’s after just one month!