you can find low-cap AKs for well under $300 (only take 5 or ten-round mags)
WASR-10s and such run for about $350 but will cost $400 after S/H, transfer, and check fees off the internet
Buying a Saiga will go about $250, then will cost another 150-250 bucks to convert it to AK-style dpending on how you do it.
Yugo underfolders will cost about $475-480 off the internt and after the extra fees, but are much better than WASRs. It's what I'm currently saving up for. If you plan on getting a WASR, then you should ask around about them to WASR owners because they can end up being bad rifles due to sighting and magwell problems. Get some info before buying one that you cant inspect yourself to make sure