Walmart offers the Duck Brand Weatherstrip Seal for Extra-Large Gaps 3-Pack for $5.25. Opt for in-store pickup to dodge the $5.99 shipping fee. That's a buck under our March mention, $1 off, and the lowest price we could find. Each self-adhesive foam strip measures 3/4" x 1/2" x 10'.

Update: The price has dropped to $4.47.