No... CD's have nothing to do with popularity. It has to do with how much money the artist and the company make for all of their time and for the production costs. If you could buy a CD for 5 dollars, that's 25-50 cents per song, when it costs at least a dollar to buy them from iTunes. And why would you buy a pair of shoes for 100 dollars when you could buy the same pair for 50?
Buy used CD's. They're all over the place, and they're as good as buying new at a fraction of the price. I've actually started borrowing CD's from libraries and dumping them onto my hard drive. I rip them at CD quality without compression, so the sound is identical to the original. Doesn't cost me a dime.