Last month, J was oversold on DFW-HKG, and they needed two volunteers. They started at a $1,000 voucher. Then offered refund of fare difference. Then offered a $1,500 voucher, plus refund. Then offered $1,500 voucher, plus J re-route through NRT.

I believe the final deal was a $2,000 voucher, overnight at DFW, and F on the next day's DFW-HKG.