Quick! Let start a subversive private mail company, like Lysander Spooner's American Letter Mail Company. His company literally compete with the USPS for business until it was shut down by the governmenet's lawyering.
He succeeded in driving down the cost of government mail.
Instead, UPS and FedEx have taken the high-margin segment, leaving the low margin stuff for the USPS. Also, much of what Lysander Spooner's company was great for is now covered by email and other Internet apps. (IIRC, an attraction was that intra-city mail was delivered quickly.)
He succeeded in driving down the cost of government mail.