Amazon offers the 3M Lens & Hard Plastic Cleaner 8-oz. Bottle for $2.18. Check out via Subscribe & Save to drop it to $1.85. With free shipping, that's the best deal we could find for this item shipped by $8. (Several stores charge around a couple of dollars more, but then tack on high shipping prices.) It removes yellowing and discoloration from headlights and other hard plastics. (Be sure to cancel your subscription after receiving your item to avoid being billed for subsequent shipments.)

A close price: Pep Boys offers it for $2.90. Coupon code "MMJ25" drops it to $2.18. Opt for free store pickup to avoid the $6.55 shipping charge.