So, USPS provides the service to the you through the vendor, but at a discounted rate. Which means they are selling the service to the vendor at a steeper discount.

How in the world can USPS justify selling their product cheaper than their old discounts? I ship almost exclusively with USPS, Fedex for heavier/bigger items. Using eBay shipping there is a small discount, but I can see why USPS would discount to them, HUGE volume potential. But, bigger discounts to that service?????