I remember when Norinco SKSs sold for $90 in the '90s, which made them mega bargains.
But $600? The world hasn't come to an end just yet. Skip it.
Mauser Werke, Schmidt-Rubin, Colt, Walther, HK, Weatherby, Browning, Ruger, Beretta, Savage, Bushmaster, Marlin, Mossberg, Remington, PTR, Saiga, S&W, Sig Sauer....a few friends of mine