Warning: I don't have an AK. But, anybody knows that an AK is scary looking, VERY reliable, reasonably cheap to shoot, has plenty of punch for human sized targets, and though not usually very accurate, easily accurate enough for home defense, etc. People say that Century rifles appear to be built by drunken monkeys but the AK is specifically designed to be built by drunken monkeys and most of the AK's they sell are just straight imports from some old Warsaw pact country anyway.
The price is unremarkable. Lots of people sell AK's so it's easy to shop around. For a start try:
Oh, and my personal opinion is that if you want to shoot 7.62X39 but don't care so much about looking scary or magazine capacity a Yugo SKS is cheaper and usually more accurate. I am currently thinking about buying a semi-auto rifle and will probably buy an SKS or an AR-15.