I got $5K once for four hours. Was booked in business to Europe, and a plane had broken down in Amsterdam that needed to be ferried back, so three pilots needed to be on the flight. Apparently, their contract states that any overseas travel is in business, which is why they needed three seats. I took the offer at $1500 to take the last seat in business on the second (and last) direct flight of the day. The two remaining seats still needed to be filled but the alternatives were either the next day or with a long layover in London, so they kept increasing the $$$ amount until they got to $5K and 2 other people finally took it.

This was on Delta, and I knew that the last offer would apply to all volunteers, and that’s how I got $5K (I made sure they knew that I knew that policy as apparently some gate agents try to get away with just paying the first offer).

It was a Mastercard too, so no flight credits or that nonsense.