You could watch the inventory of J in expertflyer. As people begin buying those seats, the upsell offer will be even less likely to move. I think an SWU is worth saving $1000 (the max you said you'd pay) on some of those routes. But only a few people probably know the algorithm that determines those upsell prices and they aren't likely here on FT, and if they are they're not going to give us an answer.