There's plenty of business opportunity in any genre; you can make a shit-ton of money by simply making the game good and building community goodwill.

The strategy is simple: 1. there's always plenty of people who are ready to spend way more money in a game than you and I would consider sane - just let them spend it but 2. make it easy to gift in-game items to other players. You don't even need to keep adding that much content - the "whales" are always happy to keep giving away to new players all the time.

Assuming you've built up that goodwill, this is all you need to keep the cash flowing. But that's non-exploitative, so you'll be missing that extra 1%. /shrug