They're lower. Not by a lot if you just look at the median, especially relative to CoL (lower rents, lower taxes), but on average, the Bay Area has some 300k tech workers (?), several companies that make over $1m in profits per employee and drive the salaries up.

In Zürich Google will make you a 250k offer, and if you aren't happy, too bad for you, nobody else is going to pay that in Europe :)