Well, terse comments aside; let me put it in most simple words.
1) If a Westerner / European is offered a salary of say US$ 5000 per months (just exemplary); he will for sure refuse becuase, he is getting the same or more in his country; OR even if not, it is difficult for him to maintain a decent livelihood back home. He will turn down the offer.
Whereas, if you offer the same salary US$ 5000 to an ASIAN (no specific nationality being pointed out here so no need to get hurt); he will be jumping out of his shoes. This will be a very good salary for him and he will come running.
So, in short, the hiring people are aware of the facts and situations back home for most nationalities and hence act accordingly.
Its all as per simple basic laws of Economics.

Nothing to worry for you FrenchMan, U enjoy your time here. Just don't look down upon any Nationality.