Amazon offers Prime members the Carhartt Men's Workwear Original Fit T-Shirt in several colors (Carbon Heather pictured) for $12.49 with free shipping. (Blain's Farm and Fleet charges the same via in-store pickup.) That's the lowest price we could find by $6, outside the below offer. It's available in sizes S to XXL.
A close price: Bass Pro Shops offers it for $12.99 via in-store pickup.