$1,000 for a comfirmed J seat a month before the flight is a pretty solid deal.

To me, this is worth more than the "would you upgrade for $X?" deals. Those offers are either in the form of a kiosk upgrade - after everyone else has selected seats - or even worse, at the gate, waiting for other people to board before you know whether you're headed for Y or J.

$1k for 15 hours is almost always going to be a hell-yeah from me, assuming we're talking about any kind of quality carrier. If I'm cash-strapped enough to make it an either/or proposition, I'd want the best rest prior to trekking/climbing. Slogging it home in Y wouldn't be as big of a deal to me.