Any company that has a product built on recurring payments will always tend towards becoming predatory in the money they need to extract because #1 they need to have pinch points to ensure they get money at regular, predictable intervals since they're a business and #2 because there is absolutely no reason for them not to turn the dial up on the micro-transactions -- up and up -- slowly until the profit gained is cancelled out by the quitting players.
This is actually limited in several ways. You can only purchase x numbers of many things per day/month, a mechanic I can only assume is absolutely intended to prevent someone from buying incredibly quantities in one sitting. If you're going to spend a lot of money it actually forces you to spread it out over many days and weeks.