How about checking out the local army surplus store? You might find some decent socks pretty cheap, at least they work for me and don't cost an arm and a leg.

BTW do you really have to carry that many pairs? As long as you can wash the socks somewhere you don't need a fresh pair for every day. I've never taken more than 4 spare pairs even on quite long trips. But I like to travel light and I always take a bar of soap. Reduces the bulk a lot as I can wash dirty clothes and underwear when necessary.