I break and drop and lose sunglasses constantly, I have to buy 3 or 4 new pairs a year so I'm not interested in buying anything expensive. Until recently I bought some Chinese 5 euro crap but I would prefer to buy 10-15 euro EU made crap. Is there anything like that available?
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.