I`d try looking on gunbrokers or guns america and see what they are going for on auction if you can find a like model. You will need the model number of the pistol besides the manufacure to make a similar comparison, the barrel lenght and finish type will affect price too.
The two sites are a good resorce when priceing a firearm.
Good luck.
http://gunsamerica.com/
http://gunbroker.com/