Re: "low cost"
Thank you for pointing out something that has bugged me for years, yet very few people know about it.
China, through clever manipulation of the Universal Postal Union, continues to declare itself a third world country when it comes to international last-mile delivery rates.
UPU rules were designed with a commendably egalitarian mindset, which is that poor countries should be able to send mail to rich countries and vice versa at rates affordable to citizens on both sides. That means it could send US$30 to send a small packet from the US to Papua New Guinea but it only costs $2 to ship the other way. There's a complicated system of rules and agreements but it basically means rich countries like the US subsidize mail delivery for poorer countries.
The issue with China is that they claim to be a first world superpower that's responsible enough to sit at all the Big Boy's tables for shaping global policies, but when it's convenient claims to be a dirt poor third world nation who needs all the subsidies they can get.
End result is that sellers in the 2nd richest country in the world by nominal GDP can ship a Box of Tat for less than $2 across the world to the US or UK while it would cost $20 or $30 to go the other way. It costs the UK and US a lot more than $2 to delivery that package at the final mile due to higher wages, environmental standards, overall costs of living etc. etc. In fact as you point out it's a lot more expensive to ship the same box from London to Liverpool or New York to LA. So western countries are subsidizing those shipments through national taxes for Tat Sellers in China to put local companies out of business.
It's crazy I tells ya!!