I paid $345 this time last year for my Yugo SKS if that's any indication to what they are worth these days. Mine appeared to be in unfired condition although there's not really any way to tell for sure. In any event it didn't have very many rounds through it. The Chinese and Russians are going for more than the Yugos (Russians are going for a lot more). Some variants are even more desirable check out Survivors SKS boards
for more details on each variant. Prices have gone way up since I bought my rifle due to the current panic. They aren't making any more of these rifles so don't expect prices to come back down.