Most of the auctions I've been to, were overseas. Bit it is likely the same or nearly so. There are regulars who attend and they will sometimes (often) run the price up on an item you are interested in, just to discourage you. They buy in bulk and play the averages.
You might want to get there early and work a deal with one of the regulars, to bid for you. They don't often bid against each other much and/or run the price up. They make there deals before hand and bid alternate lots, so everybody gets a taste. Except the independants.
If a foriegn governement is interested in a certain type of vehicle, all bets are off, the regulars will run the price way on up there. They may be acting as agents for a third party or want to corner the market in a certain vehicle or machine.
Figure out what you are willing to pay and stop bidding when your budget is reached.
If your sharp enough to pick out the Homo's, they are generally a good group to work with. No chit. Business is buisness.