I'm trying to research the ways in which games make money. I want to know more about the models they use (free/premium, trial/subscription, free-to-play with micro-transactions, etc.). In addition, I want information on which models work for which games, what models are best for which age groups, etc.
I've tried my best to find information, and Google hasn't turned anything up at all. I think I'll stop by my University's library and see if there's anything there.
This may seem like a broad question, but I'm looking for links and titles of books, not typed-out answers.