Originally Posted by
NOLAnwGOLD
KLM has a chart for upgrades at the check in counter, which has fixed miles and or $$ depending on your booking class. Also I've been offered upgrades for purchase on the AF app at check-in for cash as well (did that each way from AF PE Class W for 300 euros each one way from LAX-CDG-MAD for me and traveling companion). Never tried when it was an award ticket though.
You'll get standard STE+ services (i.e. lounge access and SkyPriority check in/boarding) but not much else.
I thought the KL chart with miles+dollars had been dropped awhile ago. It seems at this point that while upgrade offers may still be made available on day of departure, the amount is not readily predictable.