If you like playing the lotto you can buy an economy or premium economy ticket and bid for an upgrade. Depending on the loads you may get lucky. Sometimes you can even buy up to business right away on the bid upgrade platform. I've seen prices for instant upgrades in the range of C$1000-1600 from London. So if you were to buy a cheap Y ticket for around $750 and bought upgrades both ways for around $1250 each way you'd be looking at half the cost of the $6k ticket. But there is no guarantee.