It is funny you ask that question because I asked that same question myself. I was told that a standard shipping container costs the same to ship from China whether it is full of drywall or cotton balls. They apparently charge by container, not by weight.
I actually asked this question because of the influx of Chinese-made batteries that I've been seeing. Those things are pure dead weight, so I couldn't help but wonder how much cost savings there can be after shipping them halfway around the world.