I agree that this is a slippery slope. I understand that you need money to run a site, but in my experience (I'm an IT guy too) website operation costs are almost always overestimated (you admitted yourself that there is a surplus). I can tell you right off the bat that this makes me less likely to submit music in the future.
I believe in being upfront with the people who produce the content, and this was not upfront at all. The fact that you have to justify your actions (to me) means You should have let everyone know. That's my issue here. If your justification works now it should have worked in a more upfront manner. This was not an experiment. Everyone who has submitted content here feels like they have a little stake in the site. Pointing to a policy is something Microsoft would do.
I know I haven't submitted much here, but I would like to see more openness about things like this. Otherwise I might as well just stick to my soundcloud channel when it comes to posting remixes.
Then again when it comes down to it djpretzel owns the site and can do whatever he wants. From the looks of the posts only recourse is to move on if I disagree.