I use gunbroker to look at the actual sold listings for price comps.
You have to sign in, connect to advanced, and then select Completed Items, and enter a description.
Then I sort by number of bids high to low in order to get to the ones that have sold.
I have bought and sold, but that was a few years ago.
I got some good deals, and I had a couple of deals where the actual firearm did not live up to the descriptions.
When buying these days, I like to hold and inspect the firearms.