As there are only 6 seats left to sell at this point, ~6 weeks out, they will very likely dwindle down to 0 and the $900 offer will be gone, baby, gone. It's a tough one. I'd probably stay in PE versus spending another $1800. If you have 50k points and $700 you could set an EF alert in case they open C inventory for 2 upgrades. Instead of $1800 it would cost you $700 plus whatever you value 50K points. You can call and waitlist for this option.