jsinger - 3:30 am on May 15, 2011 (gmt 0)
I had forgotten that went into effect in 2009.
It applies only to very large shippers. Offhand, the savings don't seem in line with the large volume required:
"Commercial Plus prices for Express Mail will be 14.5 percent less than USPS retail prices; Priority Mail Commercial Plus prices will average 7 percent less."