I own a Romanian SAR-1 (low end of the price scale) with a Kobra optic:
It's by far my favorite rifle. This is a civilian AKM lookalike (1mm stamped receiver), made in Romania and imported by Century, with some U.S. parts added to meet the 18 USC 922(r) requirements.
Actual AK-47's, of course, were selective fire, milled receiver, 7.62x39mm; the AKM or AKM-47 was selective-fire, 1mm stamped receiver, 7.62x39mm; the AK-74 is selective-fire, stamped receiver, 5.45x39mm. Civilian variants of all three are available on the U.S. market. Strictly speaking, no NFA Title 1 civilian guns on the U.S. market are actual "AK-47's", just like there are no Title 1 "M16's", but I know what you mean.
Civilian AK lookalikes are available in 7.62x39mm (the AK-47 caliber, basically a relatively low-powered .30-caliber similar to .30-30 Winchester), .223 Remington/5.56x45mm, and 5.45x39mm (ballistically comparable to .223, more or less).
Romanian AK's imported by Century Arms are the least expensive AKM lookalikes; Yugoslavian guns are a bit upscale, and the Bulgarian guns above that.
Milled vs. stamped receiver--the Russians replaced all their milled receiver AK's with stamped receivers, not only for ease of manufacturing, but also for weight and durability. Milled receivers are HEAVY compared to stamped, and a properly heat treated stamped receiver will be just as durable as a milled one. Some people believe milled-receiver guns are more accurate than stamped, but IMHO that has more to do with the fact that most milled-receiver guns are at the higher end of the market, and hence tend to have nicer barrels (but a stamped AK with a high-quality barrel would do just as well).
If I were going to buy a new AK in your price range, I'd probably look at a Lancaster Romanian or Yugoslavian build through Atlantic, stamped receiver. Caliber choice is up to you; mag availability is best for 7.62x39mm; 5.45x39mm ammo is the cheapest (but the supply could dry up in the future); and .223's are probably the most accurate and have the most ammo choices, but are hardest to find good magazines for. The 5.45 and .223 models are reputed to be slightly more accurate than 7.62x39mm, but on the flip side, 7.62x39mm is powerful enough to legally hunt deer with in states that allow hunting with centerfire rifles.
Whatever you get, I'd suggest making sure it has the optics rail on the left side of the receiver. Even if you don't want an optic now, if you ever do get one, it's a lot easier to buy a gun with the optics rail than to add the rail later. In my experience optics make the AK platform worlds easier to shoot well; it is not inherently as inaccurate as some people believe (3 MOA is probably realistic for a 7.62x39mm model, with good ammunition), but it is an easy rifle to shoot badly thanks to the short sight radius and heavy gas piston/op rod.
