I think the 10% off could make it interesting to some. Take the couple who travel twice a year in business class on QF even sale fares around 5-8k that is at least a saving of 2k a year. Or the family that travels once a year in premium is around 12k (4 pax, 2*2 discount) all in so recoups the $1200. That said, I am usually buying on price and find QF expensive and going with JL, CX or QR.

(I think the Amex platinum is better value with unlimited priority pass, travel credits, hotel status, and the airline program tipping it over the line)