Paul - I was at Wal-Mart last night and this thread reminded me I wanted some ankle length socks. All WM's I have been to have these socks, they are Starter Dri-Star, they are 98% polyester 2% spandex. They have them in brown/tan, grey, and black and in ankle tab, low cut, ankle, and crew lengths. I think they run $5 for 3 pairs.
In the past couple months I have had several 8-10 mile days, one 15 mile day, then several 4-5 mile days plus probably a dozen 1-3 mile jogs in one of three pairs of the crew length socks like this I have and you really can't tell they have been used.
I am not a big believer of paying several times more for clothes, I think the majority of what you are paying for with clothing is the brand name. Especially when it comes to synthetic materials like polyester. Polyester is a really cheap fabric it has only recently been re-purposed and re-branded with all these flashy terms and brands.