The reason is that Sony / Fujitsu / Toshiba / etc, don't owe anything to the United States, and they WILL go to other countries to find cheap labor.
If you had your choice of two laptops with equal hardware in them, but one was $500 more, which one would you buy?
Unless of course you are looking at a Mac...
Faith may be defined briefly as an illogical belief in the occurence of the improbable. - H. L. Mencken