The only time I've volunteered to be bumped was when BA offered $700 in cash (technically I got a prepaid VISA card) and a free hotel+meals. That may be due to the EU though (there are passenger rights regulations about compensation for delays caused by the airline)

Back in the days when I traveled a lot, I would ask for some sort of on-the-spot compensation - usually, put me in first/business class on the rebooked flight. Sometimes it worked, sometimes not.

You can ask them to pay you in cash as long as you don't accept the offer before hand. They're legally required to compensate you with cash if you ask.

Surely they would just say "thanks, but no" and keep looking for suckers who will take a voucher?

Where "suckers" are people that don't like what you like?

I like to travel so I would rather take the $1000 voucher than wait for a cash offer that someone like you would jump on before I could get a chance.

I've taken in over $5,000 of free air travel over the years and always used it to visit family and see places I wouldn't have otherwise. In the meantime people thinking like you got nothing because it was a "sucker's" deal.

I suggest you look into the study of economics and pricing to understand how people can get different levels of value from things. The you might understand why auction systems like that aren't magically lining your pockets with gold.