Here's a story from earlier today:

I was at LGA waiting for a 7pm flight to BOS, at the gate next to where I was waiting was a 6:50pm CR9 to MKE. GA initially announced she needed 4 volunteers and started off with $500. Every time she announced it was DL$, Amex, or other gift cards.

Subsequent offers were $800, $1000, and $1300. Somewhere in there she got 3 volunteers because she again announced $1300 seeking 1 volunteer at that point and they would be rebooked for tomorrow morning.

IME I've never seen a $ offer so high, or it escalating like that.