For a limited time, these Quiet Comfort Waterproof Mattress Pads start at only $13.47 (for a twin size) at Walmart.com. Shipping is $4.97 or is free with your in-store pick up or $50 purchase. This is the lowest price we found for these. Additional sizes are also on sale, including Full, which drops to $17.47, Queen, which drops to $19.47 and King/California King, which drops to $24.97. Pads are 100% cotton with polyurethane backing, and have very high reviews from Walmart customers. Sales tax is charged in most states.