I love arcade autions! Super Auctions comes through my area about 3 times per year. I got my mame cabinet from them for $80 (after the buyers premium and sales tax). It was a non-working Killer Instinct 2 cabinet that had been converted. It was basically just a cabinet with a control panel so I suppose I did pick up 4 8-way joysticks with the deal. I have also purchased an Itouch5 from them at $285 (again after tax and buyers premium).
Super Auctions only has about a 2 hour preview period the morning of the auction and then the bidding begins. Typically the groupings of machines are megatouch/touchscreen games, arcade games (seperated by upright, cocktail and driving cabs), pinball machines and dart boards. Usually they start at the megatouch/touchscreen games and then move onto arcades, then pinballs.
As far as pricing, it depends on the demand in the crowd. Typically, old working classics like ms. pacman and galaga go for $500+. The 40-1 or 60-1 Mulitgames go for $800-$1200. Newer shooter games go for probably $300-$500. This past June the showcase cabinets were going super cheap $200 or so.....I guess because they are so big they have limited buyers. Last November a working almost perfect condition (had always been home use only) Gauntlet Legends went for $400.
Pinballs vary more but up until this last November auction were going for $1,500-$2,500. In November the price range was more like $400-$1200. This is a huge price drop from the typical $2000 they typically go for. I'm hoping for a similar price structure on them come April's auction.....hehe.
Anyway, as others have stated, plan on spending the whole day, unless you have a real good idea of when they begin bidding on what you want. Its fun anyway, I like seeing what games go for what price. At the place they hold our auctions there are concession stands that sell burger/hot dogs/ and more importantly beer so that keeps your energy up for the day.
I will caution this though, its easy to get carried away, everytime I go I'm tempting to just open the wallet and dish out all kinds of coin.....you gotta show a little restraint, unless you have unlimited funds and space.
One last note, it took me the last November auction till I was able to understand the fast talking auctioneer.....it was hard for me to understand where exactly the price was at certain times.