I have conducted a dollar auction (in a small group of people, many of them very clever). What happened was rather a surprise. I was selling a £10 note. One bidder offered £0.01. And then ... another offered £10.01, just enough to guarantee that continuing was a strictly-inferior option for the person who had already bid. Self-sacrificing sabotage!

I'd expected one of three outcomes: (1) bidding up to silly levels, for the usual naive reason; (2) no bids or very few bids, after seeing that the obvious naive thing would end up losing a pile of money; (3) bidding up to somewhere around £5 and stopping randomly, some variant of which is probably the optimal mixed strategy when the thing being bid for is worth essentially the same to everyone. (Not exactly the same even though payment is in the same currency, because of variations in risk aversion.)