Sorry, but revenue factors in to efficiency. Try the math again.
USPS is not in difficulty due to a failure to raise prices ~ the Postal Rate Commission turned down higher rates ~ they simply don't recognize the Issa/Snowe $5 billion tap as a legitimate postal expense!
That's Congress' problem!
Then, your boy Obama has kept the Great Obama Recession running 3.5 years longer than planned which has suppressed mail volumes.