Well Of course its discriminating. And some good companies e.g. Qatar Airways r paying equally to all the employees irrespective of the nationalities.

Second part - why this difference-
1. Its difficult to convince the westerns to come here on the same pay as asians.
2. Its to provide the averege living standard of the country from which the person is comming.
3.Asians dont have much job opportunities in their own countries so they agree for the lower wages easily.
Demand and supply rule. When a lot of people r available from a place they will be agree on less wages.

Now why to hire westerns - when the people of same caliber r available from asia too on less wages...... To make the place multicultural and to utilize the skills and experiences of the people of the entire globe.

Despite all these reasons - its off course discrimination to hire on different salaries- for the same post.

Qatar airways is paying same salaries irrespective of the nationalities and still it is having a human work force comprising 93 nationalities of the globe.