Is this just not another form of freemium?
As I remember it Western MMOs/games focused on the subscription model, aside from WoW were suffering but were aware of the Free 2 play model in Asia.
That got imported over and soon after it was shown to be viable, the idea propogated through the system
So the original model is pretty old, and that is also the first place I heard about a freemium model before it began being heard in non-gaming enterprises.
I haven't encountered other examples of freemium games of that type, that weren't utter garbage.
Like Valve, we also have a policy of not selling any items that would impact the core gameplay.