Ashes promo last year based on the 1st Test score. Australia scored 215 runs, so that was the price set. England scored 425 iirc and that was the number of seats available. Went on sale at 8am on Qantas and sold out within 3 minutes. I booked my ticket in about 40 seconds. BA had the same offer later in the day as well.

I also managed to get a friend at Qantas to put me on her Staff Travel Benefits and I flew business class for around £550 to Oz at the begining of last year. Not sure I'd want to do it again as you just don't know if you will be travelling or not until the plane is in the air! On the last leg home at HK I was told to move from my nice upper deck seat and go with the ground staff agent. Thankfully it was to a lower deck business seat!