Dunno about darn tough socks, but I have some smart wool socks i’ve been wearing for years and years. No idea what they go for now, because I bought mine over a decade ago, but whatever the cost they are absolutely worth it.

I also knit my own, and it’s the only way i’ve gotten near the same quality and durability, and the cost for that is pretty high, even without considering the time it takes to knit them.