we used to play cookie run ovenbreak a ton in high school. eventually we played it so much, we figured "hey, why don't we spend some birthday money on a few runs of the gacha? we play this game so much anyway." and then paid some more when a new character came out. and so on. it didn't become a problem, mostly only because we didn't have a job yet and could only spend money we got from birthday gift cards and stuff.
but looking back, we definitely spent more than we'd have liked. not a lot in the grand scheme of things, again we were a teenager without a job, but still. we don't play it anymore just because it became so bloated and not very fun. felt like a chore to log in every day to do the seven million daily tasks for quest rewards and event tokens. same with cookie run kingdom, although we never spent real money on that one.
the only other time we've paid for microtransactions actually isn't a mobile game! it's a petsite called pokefarm q, where there's a premium currency for certain stat-boosting items and a month-long "hypermode" that powers up shiny chances and gives you some other rewards. what we like about pfq though is that you buy hypermode with the premium currency, not actual money. and because the currency is available through trading with other players, there are quite a few users who pay for their hypermode without spending any real money at all.
we played pfq for a while before buying anything. then we wanted to do a shiny hunt, it was around our birthday, and we'd just been paid, so we tossed a couple bucks in for hypermode and some premium currency items. we plan to continue that whenever we're shiny hunting, because honestly we play the game a lot and it brings us a lot of joy to collect our silly little pokemon guys.