Several years ago (when I was a manager at Google) one of my employees needed to relocate overseas in order to facilitate coming back under a more preferable visa type, and they were looking at options. For the same role where they were earning $135k base in Mountain View, it was going to translate to about $115k in London, $155k in Zurich, and only $89k in Paris. They chose Zurich and ended up staying there for over five years before moving back to the bay area.