Offering volume incentives is a common business practice in the U.S. and around the world. Although the U.S. Postal Service offers incentives to businesses that presort their mail, the agency does not offer incentives based strictly on the volume of packages shipped. One reason might be that offering volume incentives would lower the profit margin on each package shipped; yet, the potential volume increase of items shipped would make up for the smaller profit margins.
The Postal Accountability and Enhancement Act of 2006 (PAEA) ushered in a new regulatory structure for the U.S. Postal Service. One key element was a price cap on market dominant products. (Most of the Postal Service's products are market dominant.) This means that price increases for market dominant products are capped by the rate of inflation as measured by the Consumer Price Index (CPI).
The Postal Service has more than 10,000 prices contained in a 1,800-page customer manual known as the Domestic Mail Manual (DMM). The DMM provides individual and commercial mailers with information about postal services and standards for both domestic and international mailings. The Price List, also known as Notice 123, contains domestic and international retail and commercial prices for all postal products and services.