Postal Service: Interesting facts - Azcentral The Postal Service compared its Express Mail and Priority Mail services against two competitors for sending letters and packages weighing up to 10 ounces over different shipping zones. Here's a summary of the results: 1. The Postal Service's Express Mail and Priority Mail was less expensive than comparable FedEx services in all 294 situations examined, according to the study, with price differentials ranging from about 17 percent to 77 percent. 2. The Postal Service said its Express Mail and Priority Mail was less expensive than comparable shipments by United Parcel Service in roughly half of 98 scenarios. On letters, the Postal Service was up to 23 percent cheaper. However, on certain heavier packages, UPS was up to 140 percent less expensive.