It's not FFXIV, but I believe it applies to FFXIV even more so to FFXIV. The developers of SWTOR said that with 500,000 subscribers they could not only maintain the game (including development costs), but they would also be making a substantial profit but "nothing to write home about". FFXIV's team is far smaller than SWTOR's was at the time, they are raking in money but given they're a business that tries to maximize profits, they're going to attempt to make more. FFXIV has approximately 600,000-700,000 subscribers, the substantial profit just got quite a bit larger. I believe Yoshida himself said 400,000 was enough to maintain the game and make a good enough profit for SE to keep the game running, less than SWTOR even.