Here's a few low-cost socks (though the last one is less low-cost)
Molly Mac Gear
Many folks have made very inexpensive DIY socks. All you need is a bunch of breathable material and a bit of sewing. The fanciest/nicest of the above socks is probably the last one, which is made of gore-tex. It can not only function as a sock, but replace a tarp as well.