[spaghetti]

Do salary deltas of even 100k make a substantial difference to the bottom line for large tech companies like FB and GOOG? Of course the difference is greater than zero but as a percentage of operating cost I imagine it's relatively small.

My guess is large tech companies are eager to import foreign talent primarily because of cultural and socioeconomic differences. Who would you rather hire to maintain your legacy code bases? A skilled immigrant that's thankful for the six figure salary and will obediently complete their tasks without much fuss? Or the native-English-speaking citizen who can find a six figure salary at any of his friends' companies and will walk as soon as the legacy codebase's tech stack starts to reveal itself as less-than-inspiring?