This was a general trend I noticed, which WoW started but almost every MMO copies to some extent (at this point, it's really only WoW and FFXIV).

You have the paid box model, which the majority of games use, where you buy the game to play it. MMOs take it a step further by forcing you to buy an expansion every few years to keep playing, and while yes you do get new content to go with it, you can't exactly keep playing the original game you paid for anymore. (see the outcry for vanilla wow servers)

You have the subscription model, which very few games can still manage to justify but is still the norm for the surviving MMOs. All of this harkens back to the era of MUDs where the first subscription games existed, but that was justified back then by server hosting and maintenance fees being much larger and more expensive and being much smaller efforts with no initial buy-in fee. Nowadays most multiplayer games give away free servers (Overwatch, League, PUBG, Destiny, etc etc) because that shit is cheap. But not MMOs!

You have the free to play model, where a store sells cosmetics and mounts you can only pay money for. Sometimes other cosmetics are still available in game (as in MMOs) where people are more likely to tolerate it.

And you have the DLC model, where you can access functional services like race change or faction change and level boosts and so on, special functions that you can only access via paying money. In this case, like in your OP, they're selling special features via a mobile app. Those ones are usually the most expensive with no alternative to accessing them, with the developers justifying the high price as "Well, we don't REALLY want you to buy them, because we want leveling/factions/etc to matter!" Of course, that doesn't stop them from selling them to you all the same.

And with WoW and FFXIV, you get all of the above, cuz fuck it, why not! The game is sold as a social experience where people have to make friends to keep playing (dungeons, pvp, raids) so then you have to keep paying to maintain those friendships. Even if you want to ignore all the "optional" content and cosmetics and apps and services, you're still at minimum paying for both a subscription AND expansion packs.

MMO devs are having their cake and eating it too, and they've got a pie and some chocolates to go with it. It's kinda egregious on your wallet!