.how did you calculate how much you paid via monthly sub for something that you have no idea how much will take?
bcs if you count number of months of 9.0, you are simply wrong...
you dont pay in advance, or for future content, you pay for realm access, so only logical way to count how much 9.1 "cost players" (which in itself is ridiculous but ill humor you) would be number of months between 9.1 and next patch multiplied by monthly sub (actualy variant for long sub should be used if you play constantly) plus part of game cost (probably third, as its reasonable to assume we dont get 9.3)