Our subs pay for only so much. Server hosting and maintenance, employee salaries, expansion development, voice actor salaries, model artists, music writers, music performers, and the list goes on. That stuff in the Mogstation? That's EXTRA. That's stuff that costs SE above and beyond our subs which is why it would never be made in the first place if it couldn't be sold in the Mogstation. Also keep in mind that SE is a business. They aren't looking to "break even" they are looking to make a profit. If a business is not profitable investors pull out. Profit is necessary to the survival of a business. Just look what happened to a game like City of Heroes. It was profitable... but not profitable enough to stop NC Soft from shutting it down and investing those resources elsewhere.
And not for nothing, who are you to say "they are making enough money"? You don't know anything about the finances and costs of things relating to the development of this MMO. Don't make assumptions about something when you have little to no information regarding the details.
The Aymeric outfit would never have been available AT ALL if it couldn't be sold. I don't know how many ways to say that. It took time and resources to make it wearable by the various player races and yes selling a few will recoup that investment and anything beyond that is profit... but so what? SE making more from our game just proves to SE and to investors that FFXIV is a valuable property and worth maintaining and continuing to invest in for development. No one is getting ripped off. You aren't losing something because it was put in the shop, because if it wasn't in the shop it wouldn't be available at all.
Unless you have experience running an MMO, you likely have no idea what the MONTHLY expenses for maintaining our servers are. I can tell you this from personal experience... hosting a small game server (maybe 200-400 players) for development project costs us over 1,200$ a month. This isn't top tier service, but its also not trying to rely on cloud servers (which might work for bootleg private servers but won't for any real project). FFXIV monthly costs are probably hundreds of times that.
Now my project is microscopic compared to an MMO like FFXIV. The amount of players they have to be able to accommodate, the amount of employees they have to pay to keep things maintained, the scope is staggering in comparison. And that's just monthly maintenance costs. Development costs are a whole other ball of wax. As I said before, unless you have experience in MMO development of a scope similar to FFXIV or WOW, you almost certainly don't have any idea of the costs involved.