I've got a Si that is in pretty awesome condition. The front fender is pretty scratched up on the top, but otherwise all original equipment is there and in great shape. As the story was told to me, the original owner had it back in the day, wrecked it with 400 miles on it, and put it away. Then he sold it to the second owner who never touched it and then sold it to me because he realized he would never get around to it. So here it sits, 420 miles and running great.
It had a rusty tank, gummed carb, and cracked tires. I don't think gas had made it past the carb for a long time as the plug I bought it with was still brand new like out of the package new, yet it was installed.
Anyway, one set of tires, about a gallon of evaporust, and a brain damaging amount of carb cleaner later she runs like new. Looking to place her in a new home because I really can't afford to keep a stable of peds unfortunately.
I think $600 is pretty fair considering it's got such low miles and I've done all the hard work so all you gotta do is slap the mods of your choice on (or not) and cruise.