Amazon has the 6-Pack Hanes Essentials Short Sleeve Crewneck Men's T-Shirt (Black, Navy, or Light Steel) for $21 - $5 off coupon (check "Apply Coupon") = $16 with free shipping on $35+ or with Prime (extra 5% off with 5 items S&S order).

Also available in 4-pack (Charcoal Heather, Navy, Light Blue or Ash) for $12 after coupon and S&S.