Many small shipments across the ocean are costlier than one large shipment which is then distributed locally. USPS (and other national postal services across the world) will need to increase the prices for those small shipments and make profit out of it. I can only guess that in addition to this huge quantity discounts the shipments are subsidized by the Chinese government to accelerate export. US and other countries should learn from them...
Given that in my experience, Chinese shipping times are utterly random (as little as one week to as much as 2 months), I'd expect them to actually batch all those small shipments and send them regularly in bulk on ships (with the Chinese post, not sellers, doing the batching).
I'd need to see a citation of that really, or some ballpark estimates, to give it any credence.
I wouldn't necessarily expect local-to-local shipping always to be cheaper. But I'd expect there to be at least one option where you can bring a pre-labelled package to a shipping hub and get it sent at the same or lower cost.
