From the beginning, this country decided to have a postal service that goes EVERYWHERE, including APO/FPO, inland Alaska, Hawaii and Death Valley. Some time later, we decided on a uniform price for same.
Those areas would never be served under a purely private system. It is unlikely that 1 oz first class mail (the most politically sensitive of mail prices) would stay anywhere NEAR 50 cents except in densely populated areas. Other services would come and go, like airlines in the 80s, leaving mail, instead of passengers stranded.
The USPS is also forced to have special price classes for libraries, offerings for the blind, media mail and of course the “Franking” privilege, ensuring elected officials can send news (often thinly disguised campaign mailers) to constituents.
I don’t know if it gets credited by the gov for Franking, etc., but a purely private system would need some “food stamp” type program or maybe tax deductions to offset the imposed extra expenses.
I am doubtful that the end result would run any better or cost any less.
On Mackinac Island, Michigan, for instance, UPS, Fed Ex and DHS all make home deliveries. The Post Office does not.
I think you are on to something. For decades the letter to Boise or Fairbanks could go at the same rate because they knew each of us would be spending at least a dozen stamps locally each month when we paid the light bill, water bill, etc. Now that that’s all gone online it’s kicked the legs out from under their subsidy.
Gub’mnt pays for its own use of postage, and for franking, and they pay for free for the blind and handicapped mail.