If the USPS dropped Saturday, it will have little effect on the back office side of business. Pretty much the mail volume will remain unchanged. The same number of printed bills will be handled, the same number of greeting cards, the same number of standard mail (what used to be called 3rd class or bulk/junk), and pretty much the same number of packages.

Due to the human interface issues, USPS will still have to maintain some semblance of Saturday retail window hours. In the small town where I live, retail hours have already been trimmed somewhat.

Removing Saturday delivery will save in manpower, and reimbursements for milage. To the best of my knowledge, rural carriers only work 5 days a week. So the 6th day (regardless of which day it is) is filled in via a substitute carrier. Those subs could see a drastic drop in hours of work.

But back to my original comment about back office operations... If you dumped Saturday, all the mail that would have been sorted on Saturday morning, will still be sitting there on Monday morning, waiting to be handled.

There may be savings here, but don't expect it to remove 1/6th the operating costs of the USPS.