Many? I highly doubt its many.
Mythic Nyalotha is extremely expensive and getting mythic 15 carries would be what? roughly $30 a week. I'm sure people do it, but not sure it would be many.
I buy tokens from time to time. Mainly because I don't have time like I used to, but I still raid in a guild and want to get the gear myself. I don't exactly see the point of buying your way to good gear and don't think people would be doing it in the masses