Upgrade to First at Check in?

If there are 1-2 seats left in first, will they offer reduced upgrades or just give them away?

The current upgrade offer is $900 for a domestic 5 hour flight. I’d be willing to pay $4-500 but not $900. Debating on my chances.

Update: switched my flight to Alaska and paid $450 for first class on max plane. Will use delta eCredit next month. From now on, I’m thinking it’s more beneficial just to pay for first outright rather than being loyal to one airline. So few upgrades actually happen to first and getting worst