Previously, what like in 1990? Times change, inflation, cars get rarer, more people are wanting them. It's just the way it is. Supply and demand. I recently saw a HG Monaro sell for 45 grand, and no its wasn't a genuine V8 just a 6 cyl GTS that has has a V8 transplant. Needed a complete repaint and hadn't turned the engine over in years. I remember when you could buy an XB GT coupe for around $12,000. Now everyone wants $45 grand. You get people thinking "I remember how much they used to sell for 15 years ago, so i'm not gonna pay todays values". Yeah, years ago you could pick up an old in need of restoration, Datsun or Ford or whatever for $500, but its 2008, not 1988.
A couple of grand for a rare-ish car that needs a full rebuild in this day and age isn't too much to ask.
If you can get it for $500 good luck to you. You could probably slap it straight on ebay and get 4 grand for it and go looking for one in better condition.
If you keep it original and restore it, it will be worth more than if you do an engine swap, mods, etc. It's just the way it is with classic cars. It's like finding a GT-HO phase three and stripping it, throwing out the engine and replacing it with a new V8, new seats, etc.....just on a smaller scale.
What shits me is people trying to cash in on house prices, old houses that haven't been renovated since they were built are worth three, maybe four times what they were worth when they were built. Previously they were only worth 350 grand, now people are trying to get half a mil for them.