A best bet, search for "U2671F-S12" to find the Calvin Klein Men's Cotton Stretch Hip Brief 2-Pack (pictured) in Resort for $20.99. Add two to your cart for $31.48. With $5 for shipping, that's $7.87 per brief and the lowest total price we could find for these briefs in this quantity by $6. They come in sizes S to XL.
Update: Best bet item changed to reflect a qualifying item.