Many of them are employed on expat salaries. And some even get hardship-post allowances. India is considered a hardship post for the diplomats of several countries and for many of the expats working for some multinationals. And lately, those allowances have been mounting, as India falls deeper into the hardship category. To which you can add free and fancy housing.
Some companies even pick up their house mortgages.
The gravy train doesn't stop here. Back home, they would need an appointment to see their own ceo. Here, they can meet P. Chidambaram or Montek Singh Ahluwalia at the drop of a hat. An Indian would have to call 100 times for the door to open. They also matter here.