As a reader discovered, with orders of $25 or more, Amazon offers Prime members the Levi's Men's 168 Series Striped Liner Socks 4-Pack in White/Black for $3.25 with free shipping. (Non-members can spend $49 or more to qualify for free shipping.) That's the lowest total price we could find for the quantity by $24. They fit shoes sizes from 6 to 12.

Note that this item is part of Amazon's "Add-on program" and can only be purchased with an order of $25 or more.