It's called region pricing. Manufacturers sell products for cheaper in countries with a lower income - otherwise it wouldn't sell at all there (also remember the wages of retail employees and running a business is cheaper there too).

But American (and other first world countries) retailers may not be able to break even selling it at that price due to the higher cost of labor (+ employee benefits), cost of keeping the store open, sales taxes, etc.

The problem with region pricing is people begin importing the product if it's significantly cheaper overseas. With electronic media like DVD, Blu-Rays, and video games they can get around this by 'region encoding' it (a region encoded X-Box game from Indonesia won't work in an American X-Box).

With books you can't do this (except for translating it into a foreign language thereby making it useless here) - but that takes a lot of effort so they usually just print it in English there too and hope that the majority of people purchase it locally in their area.