It is not just a matter of comparing Qantas against Cathay on respective North American routes. Both carriers have more seats between their home base and North America than the North American carriers. The competition will be between Qantas A380s and VA 77Ws, and between SQ and CX ( if SQ use A380s on HKG-SFO). I suppose Qantas and SQ have good guarantees out of Airbus for the payload range performance of the A380.