A rifle is worth whatever someone is willing to pay for it on a given day. It’s really a question of how long you are willing to wait to find a buyer.
Most of the people browsing the classified ads on an internet site are tire kickers and lowballers. Same as at any flea market or gun show anywhere in the country.
There’s no magic percentage I am willing to lose. It’s just a matter of “ how much cash to buy something else can I get out of this thing I don’t want?” I have a couple of rifles I have tried to sell that are “worth what I wanted for them.” But no one else agreed with that, and for the amount of money other people were willing to pay, I was willing to keep the rifle sitting in my safe.
If I think $600 is a fair price and no one offers more than $350-400 I will keep it. But I’d probably let it go for $500 to a WKR who was also a good poster.
A lot of the time, I have managed to buy a used rifle at what I thought was a fair price and then sell it again for the same price I paid for it. So, I end up losing the sales tax or shipping costs as a “rental fee.” But I am not in the business of trying to make money buying and selling rifles. I am just looking for rifles I think I will like and selling them again if I don’t (or if I find something else I like better).
In your case, I would look at comparable sales (finished auctions, not listings) on GunBroker. Then figure that GunBroker charges fees that add something to the total cost, but add some peace of mind to the buyer. And I would be happy to get whatever the average is for comparable rifles.
If the rifle is tricked out with scope, bipod, custom stock, etc., then I would list one price that is tricked out and one price that is bare bones. Some people like the idea of a working package. Other people won’t want to be upsold on accessories.