I have attended a few gun auctions. I never purchased anything. To me it seems that everything went for close to retail or more on some items. It was a lot of fun even though I never bid on anything.
The thing with auctions is KNOWLEDGE
Know what they have if possible before hand , study any that you are intrested in , set your highest price before you go in .
I go to gun auctions at least 4 times a year. In fact, I went to a gun auction today.
I get good deals on a regular basis. The trick is to not get too attached to a gun, have a number and stick to it. KNOW YOUR STUFF. I knew EXACTLY what the gun sells for days before the auction.
Also, indykid is correct - know the premiums and taxes. I always figure what I want to pay for a gun, then figure what the bid needs to be BEFORE taxes/fees so I know exactly what I'm getting into.
Today, got a nice 3rd Gen Glock 22 with Trijicon night sights for $350 out the door. Saw a Norinco Mac-90 AK47 got for ~$400 out the door. Stupid cheap? No..but still a pretty good price.
At the last auction, I got a Smith&Wesson M&P40C for $386 out the door. Brand New, unfired.
There are deals to be had, but you've got to know your stuff.
You have to be really careful if you bid that you consider there usually is a buyer's premium tacked on to the price, plus they usually have a dealer on hand to transfer that might not be as cheap as your dealer.
The buyer's premium more than anything is what traps people. They figure they got a reasonable deal, and then find 15% tacked on to the supposedly good deal, now making it more expensive than going to Bradis or Plainfield.