Where can I verify this? Thats looking at only the direct transport? Or also indirect transport?
Consider a hypothetical container from the US/EU going to Africa (bringing products, second hand goods, "recyclables", ...), then the container could pick up raw minerals and resources going to China, now theres an empty container in China and it has to go back to US/EU?
So the shipping company will have a bunch of empty containers at the port of landing (destination), and needs to send them back to the port of departure to be filled again.
If trade between the two ports is balanced, then the containers will always be full regardless of the port of departure.
But since trade is not balanced, they wind up having to send empty containers on the "return" voyage. Which is pure loss for the shipping company, so they are willing to heavily discount routes that have empty containers transiting.
Which are these routes does change of course, but they are often those originating in the EU / US and arriving in Asia.
Container manufacturing is very automated, so it can be very cheap to do so.
China exports plenty to Africa, no need for such circuitous shipping patterns.
This means cargo carriers have to send back empty containers to China.
As a result, it's cheaper to book a container, from, say, Antwerp to Shanghai than the reverse. The difference can be quite substantial, potentially hundreds of USD per container.
For the other parts of the trip I don't have any hard info but I would think rail and truck is cheaper in China per km when converted to USD.