Because they could.

Try running a business that doesn't have the revenues to support high wages and you'll quickly figure out why you will pay as much as possible every single time: It means you can buy your way out of hiring the riffraff. Why do you think these high paying jobs were premised on weird trivia tests and other things that had absolutely nothing to do with the job? Hint: It was a social test to see if you'd fit in to the culture.

There have always been legions of people in India ready and able to write code for practically nothing. It was never hard or expensive. But they didn't fit in socially.