Is our sub fee not enought

[Yonanja]

Not necessarily. We can assume that a month of development cost less than the sum of all subscriptions for that month.
So, with each passing month, the game's profits are only growing more and more.

The sum of total profits is growing yes. This does not mean that the game is becoming more and more profitable however. I do belive that FFXIV is most likely nothing much more than a cashcow for SE, at least atm, to help fund other endevours.