GunBroker really throws a wrench into trying to determine a value on a gun. Stuff can sell for big bank, then the same gun a week or month later will go for far less. One thing it does do, is it makes folks think what they have is worth what the top one sold for on GunBroker. This is evident at gunshows and in gunshops. You look at something and the price just floors you, and what's the first thing out of the dealer's mouth? "Oh their selling for that much and more on GunBroker". My reply to them is always the same, and it usually ticks them off. I tell them "If I wanted to pay GunBroker prices, then I would shop on Gunbroker where there is far more selection to chose from than you have here in your store, or on your table". The look on their faces is as priceless as the stuff they are trying to peddle at those hyper inflated prices. If you have a gun and want to sell it at those types of prices, then good luck to you. You can list it on GunBroker, pay the listing fees, pay the final value fees, collect the taxes and pay them to GunBroker, or you can sell it for a fair price privately on a forum or FTF and avoid all the hassle.
I think 5Wire's assessment above of an overall average price is pretty accurate, at least for what I would pay. Guns listed here in the marketplace that have GunBroker prices on them rarely sell. Guns listed for a fair price usually do. My last two I sold here were fairly priced and sold. I could have put them on GunBroker and got a couple hundred more, but why bother? In then end, I would end up with the same amount in my pocket. It's more desirable to me to just deal directly with a buyer and no fees, taxes or buyers premium, which GB also charges now.