High speed communications and transportation combined with eased trade restrictions is producing an economy without borders. The Internet and containerized cargo, both sea and air have changed the world dramatically.
Eventually this will equalize prosperity around the world, but for the time being transportation is so fast and cheap and communication so easy it makes sense to get stuff done where the cost is lowest.
The big zinger in here is, of course, pollution. One of the major differences in costs is pollution controls. Once those get more equalized, and it will, you'll see less long distance transportation of goods.