GearXS offers the Refael Collection Men's or Women's Merino Wool Blend Thermal Socks 2-Pack in assorted colors for $6.99 with free shipping. They're available in men's size 10-13 and women's size 9-11. The colors ship at random.
Of note, they're also available in kids' size 6-8 for $4.99 with free shipping. Both deals end November 2.