An average size box of diapers will cost between $15 and $25. Meijer sells many different brands of diapers for $20-$25 and sells its own brand for $15-$20. An economy-size box of diapers will usually contain between 200 and 280 diapers and will cost around $45-$50. This works out to a unit price of $0.16-$0.25. Costco, for example, sells an economy pack of Huggies brand diapers for $43.99.