There are a couple places I regularly get towers from and $5 is as low as they will go. Sometimes they are missing things and I still make a profit.

I would prefer to be able to negotiate a lower price for missing components but this is the deal i have with them. Plus they get lots of workstations and servers and to them everything is a tower so it ends up evening out most of the time.

I know that we would all prefer to at least double our investment on every deal but sometimes it isn't possible. Gotta take the good with the bad if you want to stay busy.