My theory of why tech salaries are higher in the US: the US, public and private, borrows trillions of dollars. It consumes more than it produces. Wages are higher. And so are imports and immigration. It's all a consequence of the borrowing.
If the US stopped borrowing so much and stopped inflating bubbles and re-inflating them after they collapse, consumption, wages, imports and immigration would fall.
If the US started paying down its debt, we'd be producing more than we consume. We'd be exporting more than we import and there'd be more emigrants than immigrants.
The growth industries are the most prone to bubbles. It's easier to believe something that is rising will get big than something that is the same or shrinking. So most of the VC capital goes to growth industries. Well, it would in any case, but even more so when there is an unnatural amount of capital. So that is where salaries get bid up the most.