Unfortunately this isn’t a Europe wide chain, just Nordic.

But I love their polarised fishing glasses. 8.5e (used to be like 5).

https://www.biltema.fi/vapaa-aika/kalastus/kalastusvaatteet/kalastusaurinkolasit-2000042600

I go through a few pairs a year pretty much.

Perhaps https://www.cheapasssunglasses.com/ ? While the shop is European (Dutch), I expect the glasses are made in China.

I don’t know where they’re made, but I’ve had good experiences with the Decathlon 15-20 euro sunglasses. Polarised at that price is a rarity! (I tend to lose/scratch/run into something with my sunnies on a yearly basis)

Higher than your budget (~50€) but maybe others will find useful: maybe Meller? Not sure about the production and ownership structure but they say they were founded in Barcelona

I was the same until I needed prescription glasses. My sunglasses now were much more expensive than the cheap, crap ones but as a direct consequence from that I pay much more attention to them. I haven’t lost or destroyed them despite having them for 7 years now. So my advice is splurge a little bit and get yourself some nice sunglasses. I’m sure you’ll take better care of them than of the cheap ones.

Do you care about fashion? If not, I recommend sporting sunglasses. I wear cycling sunnies, for example. They won’t break as easily if dropped. There are super expensive ones from brands like Oakley’s, but any chain sports company should also have their own cheaper house brand.

I nearly never break my sunglasses but I’m still very eager to hear more about European manufactured sunglasses in any price range. I’ve been trying find alternatives several times during past years but with very slim results.