Last year I bought my '99 F4(found it in cycle trader) for $5,000. He was asking $5500 for it, but I haggled him down. This bike was in great condition, except for a ding here and there. It only had 6000 miles on it, and I haven't had a problem with it since I've had it, which has been about a year and a half.
A good 600cc bike around the '99-'01 range, expect to see a lot of bikes within the $4500-$5500 range, give or take a few hundred IMHO.
--There is a wrong way to eat a Reese's, and I will find it.