Ending today, Groupon offers the NFL Carpeted 2-Piece Car Mat Set in 26 styles (Philadelphia Eagles pictured) for $26.99. Coupon code "TRIPLE" cuts that to $24.29. With free shipping, that's the lowest total price we could find by $7, outside of the mention below. These 18" x 27" front seat and driver seat mats feature non-skid vinyl backing.
Of note, Amazon offers these mats at similar prices, with free shipping via Prime.