Check the gun auction sites. Don't pay attention to the ones that don't have bids, just the ones that are selling. Then follow that auction until it closes. This will give you an idea of the "street" value of a gun. Except where I live. All the guns on the auction sites are too expensive in my town. Watch for the price difference between different variants of the same guns. For Example, a stainless Colt "Ultimate Python" brings a lot more than an ordinary stainless Python.