Game designer Jeff Hamilton did an Ask Me Anything on Reddit, and was asked about payment models:
Welp, this is a big question. I want to make absolutely clear that when I’m answering this question, it’s both well-written and to-the-point. So I’m going to write you up a response at lunch, probably, and post it then.
The full response is quite long, so I’ll just provide the links:
Check it out.
I’ll leave you with another quote of his:
That’s why I liked League so much when I first played it – money = cosmetics only, not mechanical power. All mechanical power (runes, masteries) is earned by playing the game.
It made me realize that the competitive integrity of the game is not intrinsically tied to the business model. The business model just creates strong incentives to damage the game’s competitive integrity. Careful process to protect game design can allow a game-as-business to succeed as best as possible, while allowing game-as-art to thrive as well.
Just something to think about when considering the business models of Dust, Valkyrie and Legion.
Serpentine's Eve 