Some advice I received from a general contractor applies to auctions: You never lose money on a contract you don't win.
I've seen FOMO and pissing matches run up bids when simply putting a value on each lot you're after and sticking to it seems best.
Leaving an auction empty handed only feels bad for a few minutes and is easier the next time.
Once upon a time, at least in person, the auction house took there share out of the sale price (the buyer's share) but everyone where I am has charged it as a fee to the buyer for at least 15 years, so consider that when setting your number.
Anecdotes:
I've been in a bidding war, hit my number and stopped, had the exasperated Auctioneer try to goad me, and lost.
I've witnessed unbridled enthusiasm make equipment sell for 80% of the cost to buy new.
Once a bidding frenzy at a fur auction meant the price of squirrel pelts doubled and my colleague made $16K snaring squirrels that year. BTW: At least in the 90's, the People's Liberation Army was the biggest buyer of squirrel fur; I was told they were used to fringe hoods on winter jackets. That may have been as case of get the pelts no matter what.