Sky-high cost of living (property prices, mostly). Shitty apartment with a commute in the bay costs $3,000/month. Starter home in Seattle costs a million plus.
It's also a vicious cycle: high tech salaries in those areas have driven up the cost of living.
> Shitty apartment with a commute in the bay costs $3,000/month. Starter home in Seattle costs a million plus.
The prices in Madrid/Barcelona are not exactly far off already (through no fault of high tech salaries).