Hobo Ninja offers the You're Killing Me Smalls T-Shirt for $9.99. Coupon code "L7WEENIE" cuts it to $5.99. With free shipping, that's $4 under today's earlier mention and the lowest total price we've seen. (It's also $6 under a similar shirt elsewhere.) It comes in sizes S to XL.
Of note, it's available in XXL for an extra $1.89, or 3XL for an extra $2.49.