Bonnie resale prices are all over the map and where you are does make a big difference, as does mileage, add ons and changes to the bike, condition and how the bike has been maintained, etc.
First figure out what it is going to cost you to fix the fork seals and anything else you need to fix: tires, etc. for you to be satisfied with the bike and factor that into your true cost.
If you are in the US, then check the average price in your area at kbb.com; then check the prices for the same model on cycletrader.com. You can check the asking prices in the classifieds here, but IMHO they tend to be too high and emotionally driven much of the time.
Monte
