TBH its even less than 17m why? Because they also count people that have gold accounts even if thats just for a few months.
I got myself 1month of gold for 3 dollars twice just because I wanted the free games (Dark Souls month, and Steet Fighter IV month)
I would never pay a fee for something that should be part of the experience like multiplayer. Its their own fault for removing the option to have player hosted servers so why would I pay for servers then? I just want to play with friends I dont care about rankings or competition or whatnot.
I will never be part of PS+ nor XLBG