Check out Walmart's selection of Kid's Halloween Costumes, which start out at as low as $4.97. Shipping adds $4.97 or is free with in-store pick up (or when you spend $50). This is the lowest prices we found. In order to see the lowest priced costumes, make sure that your results are sorted by price (low to high). This Tattooed Pirate Child Halloween Costume, this 70's Girl Child Halloween Costume and this Nurse Child Halloween Costume are all $4.97. There are additional options to choose from while supplies last. Sales tax is charged in most states.