"First, humans are still necessary - to build the factories, to operate them, to act as security guards - and the cost of those humans is still lower."

A lot of this work will be automated in the coming decades to the point where the effect of wage costs is marginal. In addition, the salaries in developing countries will continue to increase, eventually catching up Western nations. At that point the main factors are probably tax/import policies, price of enercy etc.