IOW, cheap. The trouble with the really cheap feeds is just that, they are built not to be repaired. AFAIK, parts are not even available for most of them. I'm hopeing that Jon (from H&W) will answer on this.
The "Dynamo" import brand from Servo is not too bad, but still above your minimum. The best feed out there is a BP 8F. I've seen them go for $400-500. I worked in a lot of shops where the power for the feed was you left or right arm. Having said that, I'd never have another mill without one. Same goes for DROs. But, if I was really tight on money, there are also a lot of things I have that I'd take over power feed.
Sorry, probably not really what you wanted to here.
JR