What scares me about modern "casual" games like this one is their ability to extract money from people in a methodical, merciless way. There's no proper defense for most people. I fear our society will end up in a worse place because of businesses like this one.
I'll be forward and be completely honest: I've spent several thousands of dollars on a single of these games. And I've played many of them. Some with just straight micro-transactions (eg: League of Legends skins), some straight up "gacha" or "lootboxes" (eg: Fire Emblem Heroes, FF Brave Exvius, and so on).
When you look at a videogame compared to other form of entertainment, is just how efficient they are in a "fun per dollar" point of view. MMORPGs that cost $10-15/month and people play obsessively several hours a day are way better than going to a bar to drink, money wise. But what if efficiency is tossed out of the window, how much is "fun" worth to someone?
It's likely a factor of their disposable income. But we're now at a point where adult professionals are very much part of the player base. So if a game is free to play, but has a loot box mechanic that can make it "more fun", what happens? Well, for people without money to burn in a fire pit, it might not be worth it at all, so they won't spend a dime. For the senior executive who makes 500k or 1million a year? They could blow through 5 grands in an afternoon without really caring.
So if you have a gaming population where 90% (I'm making numbers up) don't spend a dime, 9% is spending a moderate amount because of predatory practices (kids, addicts, etc) or because they like it, and then 1% spend an INSANE amount of money because they have no real "limit", you may come up WAY ahead than if you charged a flat fee and the same amount to everyone. Because the rich people are just THAT much richer to make up for everyone else.
I know I've read some articles (none that I can find to confirm my memory) where some of the smaller gacha games with a few tens of thousands of players run fully on the pockets of a few hundred people, if that.