Back in 2010, I had a college roommate who played RF Online on a pirate server with a cash shop. He claimed that the members of his guild had to spend $1-2k monthly in order to stay competitive. He was the guild leader and the race patriarch (there are like three races with distinct leader) and he said that the guild members actually collectively paid for his gear/whatever, about $1-2k monthly as well. Not sure how true that all was.
I've spent most of last year playing a korean F2P game(Dungeon Fighter Online, great game, old school 2D brawler but with some mmo aspects). I spent like 40bucks on the game early on to get started but after that didn't spend money, just played the game, enjoyed myself, they had events every 2weeks(like a lot of events every 2weeks rotating) and pretty fast patch rate cause they were catching up to the korean version with a 5 year gap due to the game being ran by Nexon NA at first, who completely killed the game then closed it, so when the korean devs re-opened the game in the west, they reset it to an old state and started patching from there.
Anyway they have a super RNG gated system to acquire the best gear in the game. Back when I played, that gear wasn't even actually useful since you could do the hardest content(the Anton raid) with less gear, especially if you played a support.
The mentality on this game was way different than anything I'd experienced playing mmos for ~20years(mostly western mmos that is). There were a lot of players there that would spend like 1-3k a week on buying "invites" which is the currency needed to farm those best items. They only farmed this way, didn't play the game much otherwise, and generally once they were done farming they would quit cause there was nothing to do, altough a few would still log for a couple hours a week to raid with their super char and feel good about solo carrying the whole raid. There were a lot of ppl buying keys for the ingame boxes stuff for random bad rewards. There were a lot of people buying costume packs they had every 3months in rotations, just to resell them ingame for gold to buy other stuff. They'd have like 100-200$ every few weeks of packs to sell. I bought a bunch of money cards to buy stuff from the cash shop with ingame money.
The worst part to me is how fucked the economy was in terms of spending real money. Even if I wanted to spend say 100$ on the game to progress faster, the amount of stuff you'd be able to buy with this amount was ridiculously small. Like 100$ would buy me maybe 2days of farming? In 2days the odds of getting even one useable item would be pretty much near 0 especially as I got more and more gear and was only looking for specific pieces. I couldn't understand how anyone would want to spend thousands on a game where thousands wouldn't even get you that far.
It was really weird.
It was really my first experience with "whales" as they're called in the F2P market. Most F2P games I played before were more reasonable, or the amount of people spending a lot of money felt a lot smaller like in poe a few people spend thousands buying packs and stuff every league, but a very large majority of the players are pure F2P/only bought a few stash, but in DFO the ratio felt more like 50/50 between whales and pure free players. And a lot of the whales were really spending stupid amounts of money, consistently every week. Like even in my poe example the whales only buy the 500-750packs or whatever every league but leagues being every, 4months or something, that's not THAT much money, but in DFO you'd often see people selling gamecards and stuff every week in stupidly large quantities.