I've never done so before, but I had an ARPG itch to scratch. 28 euros for PoE2, and it's already my fifth most played game on Steam (like, since I started using Steam and they started counting play-time). Only Mount & Blade I and II, Skyrim, and Elden Ring sit above it right now in playtime. I bought Diablo 4 day one for 70 euros, and it was a piece of shit that I never returned to after three weeks of playing (and around 70-80 hours in total). PoE 2 in EA already has more content and depth than any full release I've played in the genre, save for PoE and perhaps Grim Dawn. Is it silly to pay for something that will be free upon full release? I guess that's a matter of perspective, I see people buying "Ultimate Edition" games all the time for 100$ or more, pre-order digital titles for "special" bonuses, or shell out for skins, mounts, and other things I consider silly. Heck; look at train and flight sims and the price of small amounts of DLC, or games like The Sims, which are much the same in that regard. Gamers buy in-game currency for real money all the time, it's everywhere - I find that to be a lot sillier than paying for an EA game, regardless of whether it'll be F2P upon full release. Some of the kids at work will spend 40-50$ or more every single month on "v bucks" or "Robux", without hesitation.
My coins and stash upgrades carried over from PoE, I imagine those of us who bought the EA will get some kind of carry-over functions and goodies when the full release comes. Oh, and also, I've been paying attention to the dev talks and updates; they actually take direct criticism and opinions and adjust the game directly according to them. No other developer I can think of does this in the same way, it's astonishing how aligned they are with their community. The biggest profiles in the community went over the 0.1.1 patch notes and were all stunned to see how well they solved the biggest reported issues and balancing (but it's far from finished, of course).
With as much fun as I've been having with this until now, I can't imagine it with twice as many classes, over twice as many weapon types, twice as much campaign to beat and lots and lots of juicy endgame stuff to tinker with. Is it stupid to pay? That's up to you to decide for yourself. For me, it most definitely was not.