I take back what I said. I haven't bought every single album I've DLed, only the ones that I have listened to more than once. For instance, I DLed the latest Saliva CD, hated it, and immediately got rid of it. I thought it'd be as good as their 3rd(or was it their 2nd) CD, but it just sucked. When I hate an album, I will not buy it. When I think the album is decent, I will buy it, out of respect for the artist. I buy a lot of CDs, but thankfully I have enough money to do so. Doesn't hurt that most of the time, the CDs are 9.99 or less.
I do realize, however, that not everyone who DLs a CD can afford to buy it right away. Some CDs are ridiculously priced(like, for instance, the first Sanctus Real CD, which I bought at a local Christian store because no one else had it. That cost me 17 dollars. I wasn't thrilled, but because the music was so good, I was willing to fork over some extra money) so it makes it hard for people who are on a budget to buy those.