At New Balance, search for "N036AST" to find its New Balance Unisex No-Show Socks 6-Pack for $13.99. In cart, it falls to $11.89. With free shipping, that's $1.98 per pair and $4 under the lowest total price we could find for this 6-pack, outside of the price below. They're available in size M only.
A close price: Joe's New Balance Outlet offers them for an in-cart price of $12.74 with free shipping. Note that it calls these "women's" socks, while New Balance marks the same style "unisex." (We won't judge, bro.)