I wouldn't. It comes down to the quality of the CD. If the music was well balanced with great songs instead of one good single and a bunch of crap I wouldn't have a problem with purchasing a $20 CD. But music has deteriorated so much these days its incredible. IMO, if this were the 60's we wouldn't be having this conversation. The recording industry has become the ultimate swindler.
I already buy lots of albums, but if they were cheaper, I'd buy even more than I already do. Wherehouse Music was recently going out of business and CDs were at least half off, making them 4 to 8 bucks each. I bought over 70 CDs in 2 weeks. Now, I wouldn't go to that extreme if CDs were always that cheap, but I'd certainly buy CDs much more often. As far as one good song per CD -- I think the music industry created a culture where people are fed what to buy. People only know what they hear on the radio, and so they are limited to 2.5 to 3.5 minute songs that are the "radio-friendly" pop songs. If you go out searching for music that isn't built up for that commercialism, you'll find more albums that are consistently great.