To be clear, the taxes paid by employees are their taxes, that they'd be paying if they worked for another company or set up their own business.

Obviously there is some effect from Apple being an employer in increasing the overall employment rate, but there's a reason Apple needs local employees to hawk it's products. If they weren't employing and selling locally, some other company would be employing those people and taking Apple's market share.

Are there any statistics about how much of the value produced by professionals abroad actually flows back to the country of origin? Intuitively, I would say it is very little because why would you return once you live in much more privileged circumstances.