People in here seem to forget one thing: PoE is running on a cycle. 3 month cycles if everything goes as planned. This means, that their earnings aren't a constant stream, but come in bulk in (what I assume) is the first month of each league. So really they only have 4 months of heap revenue with smaller streams inbetween.
The reason mobile games (i.e. Gacha Games like Genshin) or games like League of Legends, Fornite,... can get away with small prices is, that you can play them all year. There isn't really a "bad time" to play League with your friends. Every game is a fresh start. In PoE, you have a lot of barriers to even get going, which probably turns away most "casual players" anyway. What you are left with is highly invested players that usually don't want to start when the league is almost over. Those people are your customers. And those pay at the start of the league.
So really, what GGG is doing here is the (what I assume) only profitable way to sell MTX. You're not going to buy 10 sets in one month. You can only use one at a time and you're probably going to stick to one set for your character. Idk of anyone that changes MTX every other map. If you cut these heap purchases down to the more acceptable price of 20$ (which would equal to a high tier skin in LoL for example), they cut their revenue by 66%. Sure, some may buy one or two more, but not guaranteed. At best they go even, but that's unlikely.
And after all: You SUPPORT them with the SUPPORTER PACKS.
May I remind you we play a game that has 4 new leagues / content drops a year FOR FREE? People pay 13-15$ PER MONTH, just to play WoW? Not including, that you have to BUY expansions aswell. I've never played WoW, but afaik they don't get skins for their monthly subscription.
If you think that's expensive and/or don't have the money: Don't buy them and enjoy the FREE content drops a year for this amazing game.
I buy MTX to look cool, yes. But also to pay for the experience I get. Not even 2 full years and it's already probably my second most played game, just behind 11 years of League of Legends.