I understand making a profit, avoiding paying taxes, avoiding the paper trail, and the difference between asking price and buying price. I just felt with my 30 plus years in retail sales, that seeking 60 percent of new would still give them enough room to make good money on it, ecspecially seeing how I've bought three other firearms from them in four months.
If you are trying to trade/sell at a gun shop, I would try Plainfield Shooting Supply. They have given me the best trade values and I directly compared to at least one other highly regarded shop. PSS offered triple what the other local shop did on at least one of my trades. As others have stated you will do better in the classifieds.
Everything I learned about the used gun market, I learned from the used guitar market long ago.
Private sellers always want way too much, sometimes dang near new price.
Retailers won't ever give more than 50% new price, unless it is something truly historic or rare, because they usually mark them at about 75% of the new price...sometime more.
There are deals to be had in the private used market, but usually not so good that you couldn't just save up for another paycheck or two and buy one new :-/
And when it comes to selling used, I always took a hit on my item...
Ouch!
Went to a LGS on the far north side, to trade in a 160 round, 2 month old pistol. Was told they would give me forty percent for what I purchased it for. What a huge contract between buying it from a Facebook group where a used piece will sell for 90-95 percent of new value.