You almost never get a fair price when you trade. The dealer has all the advantages. So in reality when you think you are getting a great deal on that nice new handgun you have been eyeballing, in reality you are likely getting ripped on the trade. If you need to raise some funds for a new purchase and are set on selling one of your guns, just be a bit more patient and sell the gun in a private sale where you are more likely to get a fair price for your gun. But that’s the problem in our society.....everybody wants instant gratification. But all too often comes buyer remorse at a later date! That is why so many people buy guns on a whim and don't do adequate research and due diligence, then want to “trade” after a few months. You are just throwing money away IMO. You are better off in the long term buying a larger safe and keeping your guns and just buying what you want outright when you want a new firearm.
PS: I have done it before but I now regret it....learn something from your past mistakes is what a wise man does.