VOLUME is why.....there are 360 + million people in the U.S., and there is more competition, mostly in manufacturing, plus retailing, so tho' you sell for less, there's a hell of a lot more sales to be made, so plus dollars to be earned. Of course transportation costs are all part of the factor.
Now, there's more Chinese and Indians anywhere else in the world, so greater volume. However, under a country (communism) where the Government controls virtually everything, they can to some extent control pricing, but that also creates black market knockoffs!
Here in the Philippines, certainly in provincial towns and I'm sure also to some extent in Manila, the vast majority of the general public buying in the computer world, are not paying Microsoft and other software prices, PIRACY thrives!
Off course Linux & Ubuntu stuff is free, except hardware, & most of the comes in from China (Family trade thrives here!).