HobbyKing's done it again. Check out this deal: their mini-quad with four motors for $33.95! (Or $31.95 if you just let your browser sit open on that page for a few minutes).
All you need to add to make a RC quad (in addition to your regular RC system and LiPo batteries) is:
That's $90 all told. Now, in fairness, this is a pretty crappy little frame and it won't last past a crash or two. I also wouldn't expect too much outside in the wind. But what a great way to get started!