You don't have to be that old to remember when firearms were cheaper than they are today by quite a margin. We've all seen crates and crates of them at cheap prices... 10 years ago. Even two years ago, but not today. Everybody could get piles of these guns in the eighties for a little bit of nothing, but that's twenty plus years ago and times have changed, unfortunately.
I wish I had a time machine to go back and get an SKS for $100 (regardless of whatever you think they're worth in imaginary currency) but the fact is, if you're buying one for $100 in America today you'd better wear gloves because it's probably hot and if you're selling one for $100 you're an idiot or a thief. Unless things change and we let the chinese and russians flood the market with these guns again, the days of the $100 SKS are done.