usps next day cost refers to the cost of USPS services for overnight delivery, such as Priority Mail Express. The price for next-day delivery depends on the package size, weight, and destination. USPS offers flat-rate pricing for Priority Mail Express, which can help save costs on heavier packages. However, for smaller or lighter items, it’s essential to compare rates to determine the most cost-effective option. Additionally, USPS offers a money-back guarantee if the package is not delivered by the promised time.