Can you cite links to the exact financial reports that showcase the budget for each expansion? Would be an interesting read to analyze and help back up your claims, since I would find it hard to believe their budget has remained identical since Stormblood, especially factoring in inflation since then along with rising salaries & cost of technology.
The reality is it doesn't, but it's not entirely untrue either. Mogstation provides a necessary evil to the game: moderating sub costs. Ever wonder why when factoring in inflation, the sub cost hasn't risen by the roughly $5 inflation says it should have in the past decade?
Allow me to let you in on a secret in most software development: regardless of player numbers, the sub price is woefully underpriced from what it would actually need to be. If the game was purely operated on sub prices, it would literally not be worth the financial investment for Square to continue development for it without a major sub adjustment. Almost every service out there that offers a subscription prices it so that the sub will cover the basic operating costs to break even assuming X number of users. The companies make the majority of their profits through alternative avenues, like ads / data selling/handling, etc. Like let me paint a picture here: On the Assassin's Creed game I was a developer for, Nearly 80% of the game's profits came from micro transactions. If the game had been viewed by investors purely on its box/digital sales, the game would have been a colossal failure.
It's why you see the prevalent rise of microtransactions / free to play models in this day and age - box / sub price isn't profitable on its own anymore. Supplementary methods of income from a game product releasing into the AAA gaming space are effectively a necessity these days.
Raising the sub price to it's profitable value is also not a valid option for plenty of companies and is often done as a means of last resort, since by increasing the price of the sub, you will by nature automatically price out a subsection of your userbase, a risky move where the extra profits must offset the lost revenue.
The only reason FF14's sub price hasn't gone up is purely because the mogstation allows a single whale to pay the sub cost of hundreds, if not thousand's of peoples of subs each month. It also makes the game look way more appealing to the board of directors as an ongoing service product to continue supporting, despite it's extremely high operations cost from worker salaries to tech upgrades/etc. FF11 continues to get away with what it does due to the fact the game is operated by a skeleton crew, meaning its operating costs are extremely low in comparison.
That being said, back to the topic that appears everytime they add something to the mogstation. So let's run down the usual list of points people conveniently like to forget, shall we?
-The mogstation team that worked on this is entirely separated from Yoshi-P and his development team with only minor interactions between them, it doesn't detract from FF14 development at all.
-Adding on to the above, there is no guarantee that if the mogstation ever existed, this would have ever been in the game. full-stop. In reality, Yoshi-P more than likely has to sign off on a mogstation project to make sure it doesn't interfere with the main dev team's plans. (I.E: making sure if Yoshi-P wanted to include a Shadowkeeper mount at some point, that the mogstation team wouldn't make it.) Which means anything on the mogstation was never going to be in-game naturally, as it had zero development plans on the main team.