Target offers the Filtrete MPR 1000 Allergen Defense 10x12" Air Filter for $6.24. Order via subscribe to drop it to $5.93 and bag free shipping. That's a savings of $11 and the lowest total price we could find. It lasts up to three months.

Be sure to cancel your subscription after your order ships to avoid being billed for subsequent shipments. Need a different size? Note that Target also takes 50% to 70% off select other sizes, although most options are available in retail stores only.