Who buys CDs anymore? Especially when you can just spend a buck or two online and get the songs you want... I can probably count on one hand the number of actual physical CDs I've purchased in the past year.
Mr Cheapo is a better option than buying new CDs, but still, for your money, you're better off just buying your tunes online.
What a place like Mr Cheap does well - something no online store can quite replicate yet - is the browsing experience. You never know what you'll come up with just digging through piled of used CDs.
Sure, some of it is garbage. Most of it is. But sometimes you'll come up with a gem like, I dunno, Gwar's first album or something.