Auctions of guns tend to be crazy for a few reasons in my opinion.
1. For the local in-person auctions, there’s a perception among many that because it’s an estate sale it therefore is a private party “off the record” sale, rather than a transfer through a true “gun dealer” which goes into a database. A lot of folks will happily pay more than retail because they legitimately fear that the government will one day come for their guns, and they see buying at auction as a way to add to the collection (armory?) without sending a flare to alert Big Brother.
2. Online auctions mean you’re competing against other bidders all over the country. Good chance someone out there is richer, and more inclined to instant gratification than you.
3. All auctions, but especially the in person/live bidding kind, have a fever pitch excitement that causes people to lose their heads somewhat. This is magnified by guns because most “gun guys” are not just casual users of the tool who might be happy to pick up a spare firearm but really couldn’t be bothered… like the guy who is bidding on the flat of old screwdrivers, or the spinning wheel… bidders on auction firearms tend to be enthusiasts, which makes them inclined to bid with their heart, not their head. Ego undoubtedly plays a part too because guns are a very masculine item in general and it’s easy to feel “beaten at being a man” if someone else beats you at an auction on something you associate with your core identity. This causes guys to bid more than they otherwise would.
4. There’s a lot of less informed people who bid online (proxibid, liveauctioneers etc) because they’ve heard this is a great way to score a deal. That may have been true 10 years ago but not any more. There’s also a lot of dedicated collectors who use this avenue to find items to fill holes in their collection, and will pay whatever it takes. See #2.
5. There’s always going to be a dealer (or 5) bidding on any sizeable collections. They know they can mark anything up and eventually sell it so if a gun is even a slight bargain they have a vested interest in acquiring if they can. It’s not as true of other items because there aren’t many dedicated used-tool or furniture dealers. The valuable and portable nature of guns encourages flipping.