Amazon offers its Prime members the NFL Men's Inside Line III Crew Vintage T-Shirt in 28 5 team colors (Pittsburgh Steelers pictured) for $9.80 with free shipping. (Not a Prime member? Orders over $35 qualify for free shipping; otherwise it costs $5.58.) That's the lowest total price we could find by $18. It's available in sizes S to XXL, although not in every size/color/team combination.
Amazon offers its Prime members the NFL Heart and Soul T-Shirt in Charcoal Gray with prices starting at $14.99. At checkout, it falls to $12.74. Plus, Prime members qualify for free shipping. (Non-members can spend $35 or more to receive free shipping; otherwise, it adds $5.58.) That's the lowest total price we could find by $7. It is available for most teams in sizes S to XXL.