Originally Posted by https://www.alaskaair.com/content/mileage-plan/membership-benefits/premium-class-upgrades
I purchased Premium Class, but was upgraded into First Class. Will I get a refund?
Members upgraded into First Class will not receive a refund for purchasing Premium Class.
It's not the exact same scenario because you are paying for First Class, not being upgraded, but it is similar.
FWIW, I'm being quoted $161 to upgrade to F for AUS-SJC.