Amazon offers its Prime members the Hanes Men's Classics Full-Cut Pre-Shrunk Brief 7-Pack in White from $6.71 with free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $5.48.) That's a slight drop from yesterday and the lowest total price we could find by $5. They're available in sizes S, L, and XL.
Note that select sizes have an estimated shipping time of two to four weeks.