Golfsmith offers the Snake Eyes Men's Dry-18 Short Sleeve Moisture-Wicking Polo in 10 colors (Blue pictured) for $14.98. Coupon code "FREESHIP" bags free shipping. That's $15 off list and the lowest total price we could find. It's available in sizes S to 2XL, although not in all size/color combinations. Deal ends July 31.
Update: Even better, add two to cart and the price drops to $19.99. That's $10 per shirt and the lowest total price we could find for two.