what's going through my mind when i buy diadem:
90% of the time: winning the diadem gives a gold equivalent this turn (or silver, if i can't resist playing a terminal in my hand) and this gives me another province this turn.
5% of the time: um, there's no other prizes left, my deck is filled with curses from my opponent's followers, i should really just resign, i guess i'll take a diadem??
4% of the time: i know i should take a duchy, but i'm mega-winning and i just want all the prizes.
1% of the time: fishing village + UCS + diadem = win.