In that case it would be a simpler mental model for the user to just decouple the usage cost from the game cost aka the World of Warcraft model. Why let the original purchaser play as much as they want, cap their usage too (~40-50 hrs of playtime for free) and charge them for usage beyond that. Also if the cost of running servers is so high and such a big drag,why dont they let third parties run game servers and charge a fee. That way competition among game server hosting companies would bring the price down closer to what it should be in the real world.