The American Express Platinum card (that's the real Platinum card, not platinum-colored affinity cards that they issue in cooperation with Delta, Hilton, etc.) gives you a discount of up to $2,500 on the second business or first class ticket if you buy it through AmEx. That's way more than the $450 annual fee for the card in the U.S. They have this arrangement with a lot of airlines, though not every airline. If you happen to have that card already or qualify for it, that might make buying the tickets practical.