The search function won't be too helpful with "AK" as a search term, since the search engine ignores terms with fewer than 3 characters. Anyway, here's it in a nutshell:
Romanian AK's: These include the CUR, SAR and WASR lines. The WASR is the one most available right now. Cost is approx. $350. WASR's are originally made to accept only single-stack magazines, and have their magwells widened by Century Arms to take full-capacity mags. FIt and finish on these rifles is generally poor by Western standards, but they do work. Typical accuracy is in the 4-5" range at 100 yards - some do better, some do worse.
Chinese AK's: No longer imported, these are generally very well made. Norinco MAK-90's are still available NIB on Gunsamerica, etc for $350-450. MAK's are great AK's, but many don't like the thumbhole stock (the thumbhole can be changed out legally, but that's a discussion for another day). Pre-ban Chinese AK's are some of the best of the breed, generally those by Polytech are thought of better than those by Norinco. Prices seem to range from about $600 for a typical Norinco pre-ban with fixed stock to $1100 or more for a milled-receiver Polytech Legend.
VEPR: The VEPR is a Russian-built AK sporting a thicker RPK receiver and a heavy barrel. They are renouned for their accuracy. Some do not like their forward-heavy feel or the fact that they will not accept standard AK furniture. Very high quality. Generally in the $500 range.
Bulgarian: Very high quality AK's, usually built on a forged, milled receiver. Arsenal makes a variety of these AK's in various configurations. They range in price from $500-900. Arsenal is phasing out their milled receiver rifles in favor of stamped iterations right now.
The big question is what do you want to do with it? For fun blasting at the range, the WASR is a good bet at low cost. VEPR's are great if you insist on the greatest possible accuracy and you don't mind a heavy AK and non-standard styling. Arsenal AK's are accurate, built like tanks and have traditional AK furniture, but they are expensive.........
This is just a start. I'm sure others will be on their way soon with more advice.
HTH,
vanfunk