You guys are missing the point. Better established artists have a greater fan base and can attract more attention to a project. While it would be ideal to fill up an entire cd with lesser established artists, the odds of selling your tracks will increase if more people end up looking at a project.
Lets look at a hypothetical situation. PX9 only submitted one song back in 07. To this day it has over 57,000 downloads and 395,929 listens. Look at your latest track. Compare the amount of downloads px9 had on that one song to the amount of downloads you've accumulated in total for all of your songs. I'd be damn well impressed if you had even half the number of downloads that one song has.
Fact: working with bigger names will help you out in the long run in terms of what it can do for exposure. It sucks to sacrifice space on a project for people that might not necessarily "need the exposure as much," but when it comes right down to it I really doubt amateur producers need commercial exposure.