At this point I ask a student for a dollar. I hold the dollar high and tell the students that I'm about to auction it for real cash. I also tell them that this auction is slightly different from the usual auctions. The difference is that the second highest bidder also will have to pay his bid as a penalty for chickening out, and he will not get anything in return. The bidding starts.
Hands go up.
Immediately someone outbids. The outbidding goes on till the highest bid hits about 50 cents. From this point onwards it usually becomes a two-horse race. I look at the second highest bidder, who is in a mild state of shock. You know you can reduce your loss by outbidding again.