I've seen some very lucrative offers. Like $500 credit, upgrade to first class tomorrow, AND a 4-star hotel room. That might not be the norm, but that's a pretty amazing deal.
A few people took the offer, I didn't. As a result they denied me boarding and gave me the exact same deal, except it was a $1250 pre-paid credit card. I never expected to be quite so happy about not being allowed on a plane.
They were asking everyone and most people refused. I should have bartered harder to get an upgrade to business.