Perhaps they will be able to get to the bottom of how Amazon
has China and Hong Kong sellers who can ship parcels through USPS for less than the rest of us can mail a first class letter.
ePacket is a USPS program which gives some countries a deep discount for 'volume'. Frankly, I do not understand why a 'volume' principal applies to USPS. While it may be able to receive a container of parcels from off-shore, it still has to sort and distribute them through the entire USPS system. It is not like the entire container flows through the USPS system as one large shipment.
Even uglier, the ePacket discount is 'one-way'. This allows sellers in China and Hong Kong to dump bad products into USA with little worry that the product will ever be returned. The return postage often is 50% or more of the price paid for the product.
Washington has been 'looking into' the ePacket deal for years. In 2015 the USPS reported they lost $75 million thanks to ePacket (according to testimony of David Williams, inspector general of the USPS). He also reported that in 2012 USPS received 27 million ePackets and they lost an average of $1.10 on each one.