Like you mentioned, prices are stupid high and there's nothing 'micro' when decent cosmetics run $40+ and a single full effects set is $150+.

Yes, they're mostly cosmetic and QoL items for sale, but they certainly don't feel optional if you've ever played any other RPG or loot-heavy game. PoE's 'micro'transaction system is much closer to a paid mod or DLC model. I stopped because it's pretty clear that what their system lacks in straight gambling mechanics, it more than makes up for in sly psychological tricks. I have ~80 hours in PoE and started because it looked fun and the microtransaction system seemed reasonable. Looking through the store now, what I would consider to be 'mandatory' for someone investing significant time into the game comes out to about $70. They have (rightfully earned) one of the best reputations among game developers, but their insistence on selling (what should be) standard game features as $15 microtransactions is absurd. Not to say that PoE isn't one of the better F2P models out there, but GGG shouldn't get away with pretending to be a small indie studio when they have >100 employees and sold a controlling share to Tencent for >100M NZ$. Even then, your best bet for listing items for sale without premium tabs is to use a 3rd-party tool to generate a forum thread. Sure, you can technically play through all the content without microtransactions, but have fun organizing the 159 different maps, 104 essences, 42 (ordinary) currencies, endless cards, and all your actual items with the four default 12x12 tabs. Since 2.4, many of the 3-month content updates (which are always either good content or at least good-faith mistakes) have introduced mechanics which effectively require more microtransaction purchases (see 2.4, 2.5/3.7, 3.1).

For everyone else, microtransaction tabs are 100% mandatory to progress without spending inordinate amounts of time managing scarce inventory space. If you approach it as a casual single-player game, it is certainly a wholesome free-to-play model.

Path of exile inventory space