The payment model used in Starcraft 2 - a ancient game at this point - is sophisticated. A good illustration of the old game-economics model fused with the new. Oldest single player content is free; multiplayer is free; newer content and cosmetics are purchased in-game a la cart.

Instead of paying $45 one time, you might spend $120 over the course of a few years.

I suspect that will include game time tokens for WoW that can be then sold for ingame currency or used for gametime.

They also basically converted a big chunk of their subscribers to pure mtx players with that move further muddying the signal.