D1 awards go for 246K miles for Fri-Sun flights with Amex discount (Mon-Thu flights have slightly cheaper D1 award levels available just as they have slightly cheaper D1 revenue fares) and PS goes for 119K miles. The online seat upgrade pricing is not based on fare differences and they will not necessarily ever give you an offer that is less than just paying the fare difference. Online seat upgrade offers often coorelate with fare bucket availability and the flight is currently Z9, so I wouldn't assume offer will necessarily go lower.

Not much difference between 246K miles vs. $2970 vs. 51K + $2150. You are getting about 1.2 CPM in value for miles with that pricing which is roughly average for awards.