How much was the original price? In the open marked it all depends on how in demand the gun is. About 20-25% off is usually a common depreciation on a used gun in good condition, and that is still dependent in part on if you got an average deal on it. If you get a great deal then maybe less % loss. Check the used gun prices on line and check in your local store to see what retail is on a used one like yours. That will give you an idea. In the end a deal with a friend or relative should always be the amount that both of you feel is a reasonable deal. If you can’t get there sell it to a stranger for market price and tell the friend or relative to go find a good gun and help them shop. Better to forget about the deal than to have hard feelings between friends and relatives.
More ammo! I need to shoot something!