back in March at LAX. they were offering upgrades to CC for 300$. but 2 weeks later that wasn't an option. I don't have much more info than that. but it is a good deal even if its just for CC.
a few weeks later my parents couldn't get the same offer.
on my flight on June 7th out of LAX. i couldn't get any kind of upgrades miles or cash, nothing was available. i overheard TK employee mention there was only 2 empty seats on the whole flight.