ExOfficio via Amazon offers Prime members the ExOfficio Men's Give-N-Go Boxer Briefs in White for $14.30 with free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $5.18.) That's $1 under last month's mention and the lowest total price we could find. (They're a current low by $10.) They're available in sizes S or XL.
Of note, they come in White in sizes M, L, or XXL for $14.54, and in Black in S to XXL for $15.57 with free shipping via Prime.