At this time with the current gun buying trends you relisticly won't find any AR for that.
CMMG's are running 600 for just the upper right now, I just ordered one.
For inexpensive look at Fun shows, or by the pieces, (lower, upper, etc) and build it yourself. Thats always been the cheapest way.
I don't think you will be bale to find a fully assembled AR for less than 800, and that will be a lucky find.
Good Luck, lots of people buying the black rifles right now.
NRA Life Member
DRAKE: End of story.