Under Armour via eBay offers its Under Armour Men's Not Your Bro Shorts in Black/White for $17.50 with free shipping. That's $17 off list and the lowest total price we could find. They're available in size S to XXL.
Lord & Taylor cuts up to 60% off select Under Armour Men's and Women's Apparel Items. (Discount is as marked.) With items starting from $9.20, that's tied as the best deal we've seen on adult Under Armour items from Lord & Taylor, yielding a number of price lows. Shipping starts at $5.95. Some sizes may be limited. A couple of best bets: