I was flying over the holidays, and on the way back, they asked for volunteers to be put on later flights. When I heard that they were offering $600 gift cards, I volunteered. Turns out that in the end, I got $800 for getting home 5 hours later than I originally planned.
I would not have done this for only airline miles/a flight at a later time as I have found out that I usually don't get to use those. But they were offering $800 gift cards. I got to choose from Target, BestBuy, Amazon, and 13 other gift cards.
Bazinga!! That reimbursed me for my whole flight, all the meals I ate on the trip, and left me with some profit!