If it were possible to buy the USPS, what would the net worth of the whole operation be.
Fiscal Year 2003 first quarter financial report. Good luck. 
http://www.usps.com/financials/_pdf/2003Q1.pdf
Page O’ Financial Reports.
http://www.usps.com/financials/
Under what conditions would it be put up for sale? Would it maintain a statutory monopoly over first class mail delivery? Would it be free to set its own rates, and to charge discriminatory rates so that mailing a letter to Alaska would cost more than sending one across town? Would it be free from political interference, so that small town post offices could be closed? What types of labor contracts would the new owners inherit? Would the new owners inherit the $62 billion in liabilities on the books today? Without detailed answers to these questions, one can’t assign an accurate value.
But a stable business with a decent profit margin ought to be worth close to its annual revenue of $60 billion. For purposes of comparison, FedEx has annual revenue of $22 billion and a market capitalization of $16 billion.