Our mailman in our work mailroom said that their commercial rates are peanuts and that they only charge the public as much as they do because they'd prefer not to do deliveries for average Joe.
He says a lot of things though, could well be BS for all I know.
Given RM recently dropped their price on 2nd class small packets shows they are competing for business.
The Post Office group which is a separate entity from RM will also play a factor in the price charged. Running 12,000 branches isn't cheap.




