Sorry if dumb question but does Delta ever sell last-minute upgrades at the gate?

I fly on AC and see LMUs all the time where people pay to upgrade right at the gate. Almost 9/10 times it's overpriced and no one buys it but I have seen some decent offers sometimes.

I know DL offers upgrades at check in but what about at the gate?

Or would they rather upgrade 9 people and make no revenue (which is what happened on my ATL-SFO flight 2 days ago)?