Also worth reading into "Universal Postal Union", an agency within the United Nations that is responsible for managing postal service policies for its member countries.

"Under the current UPU’s treaty, China and other countries deemed a 'developing nation' receive a lower rate for packages shipped to the U.S. via the United States Postal Service."

That's why it is convenient to get $3 iPhone case from Chinese/Asian country seller at $0 shipping cost. Gotta love the loop holes, eh?