I rarely turn a profit on my project machines. It's happened once or twice, but most often I take a loss on them. Then again, I'm guilty of trying to fix and restore them to a level that's probably not realistic if I ran it as a business. Rebuilding all mechs, replacing every ramp, broken plastics, new posts, etc., etc. etc.
That being said, I agree that deals are very hard to come by. They usually aren't within the pinball community. It's usually someone who has this old, broken machine in their basement and just wants it gone. But once it hit's FB market place, it's no longer a deal as the sharks start circling....