It's not that no fees go to the USPS, but the fees that go to the USPS are pre-negotiated by the Universal Postal Union (UPU), which is a multi-national organization within the UN that the USPS is a member of.
China is considered a Group III country by the UPU, which is a "mid level developing country". Other countries in that group include Brazil, Mexico, and Thailand. The US is a Group I "Industrialized" country. Shipments from a Group III to a Group I country equate to about $1 - $1.50 USD per pound (it's not a linear scale and per/lb rate fluctuates based on total weight).
China is considered a Group III country by the UPU, which is a "mid level developing country". Other countries in that group include Brazil, Mexico, and Thailand. The US is a Group I "Industrialized" country. Shipments from a Group III to a Group I country equate to about $1 - $1.50 USD per pound (it's not a linear scale and per/lb rate fluctuates based on total weight).