I buy stuff all the time via Auctions. For our farm and company. I buy everything from Tractors to heavy duty trucks.
The key to an auction is not spending too much. Go in with a price figure that includes worse case scenario. I just bought an International 9200i Eagle, day cab with a cat engine.
I spent exactly what I had in mind, because it was a good deal even if I had to do major work to it. (Which, fortunately I didn't.) Yes, it needed work done to it. Yes, it needed body work done to it, and with 700,000 miles on the clock, being in the trucking industry, I know what I was dealing with. Frame scaling, brakes, tires, body work, rods and mains.
Exactly what I did to it and exactly how I had it priced. I had the frame stretched anyways, I always do brakes (put US made drums on), the body work I planned on and the rods and mains I planned on.
It worked out perfect.
Being a good auction buyer is simply this: Do your homework, know what you're looking for and at.
I've seen people pay retail price, for a 9 year old brush hog. (1300, had the original price / receipt with it of 900...)
I've also seen a Massy 2410 with a loader, backhoe and mower, go for 13,400 this past summer - it had 74 hours on it. (Wish I had the money)
You, the BUYER, are responsible. You're buying a used piece of equipment, unless it states 'under warranty', you have to accept it. If you're save 10% or 20% off retail price of brand new - not worth it. If you're saving 60-70%+? Worth it. People pay way too much because they get auction fever.