from another aviation forum:

"Bose is giving a $300 rebate on all there New A20 headsets if you exchange your older Generation 1 headset. This isn't good for any other Bose headset. This is because they are no longer servicing these older Gen 1 headsets.
There is no limit on how many you can return, and I happen to have about 40 pairs that anyone can buy for $100 shipped. These headsets have cut cords, but condition is not a factor on the rebate.
If anyone is planning on buying a new pair of A20 headsets, here is your chance to save a few bucks.

You can call BOSE 1-800-999-2673. Ask to get transferred to the aviation side, and ask them about the $300 rebate on the Gen 1 series headsets. They don't make any effort to let you know about the rebate, you just have to ask."