But old hardware of around those specs are still pretty easy to find at least in my area for 200 euros for a full system.

It's a little more expensive here in the US, for whatever reason.

But, still, 200 euro is a marked difference from how it was not that long ago, where I'd show up to pick up one old Dell, and would forcibly have to refuse to take the other 20 with me, even though they were being offered for free.

My favorite bizarre thing was a G4 Cube on Craigslist for $20. I was all over that, and went to meet the dude at the storage locker he had it at.

Dude then offered me 6 G3 iMacs, and 5 G3/G4 towers along with the Cube for the same $20. I sure as heck took it all, but that's absolutely not a thing that happens anymore.

Now it'd be a couple hundred for the Cube, and they'd try to sell each other mac for $150 on top of the Cube's price, or like, more, if they just look at eBay listings for the pricing.

I'm certain that new retro stuff will stop being more than old computers sooner than I'd like, since you're right about the upgradability and, well, the charm. A shiny metal box is nice, but I'm a fan of ugly beige things that are 6 different shades of beige and beep and whirr and make all sorts of annoying noises.