For a limited time, Adult Halloween Costumes drop to as low as $9.80 at Walmart.com. Shipping adds $4.97 for orders under $50 or is free with in store pick up. Choose from many adult costume and accessory kits for men, women and teens! This Maid to Order Adult Halloween Costume drops from $14.97 to $9.80 and this Pirate Mens Halloween Costume is $9.98. Sales tax is charged in most states.