"A lot" if you measure in absolute numbers. Very few if you measure in percentages. Remember, the median salary for a tech worker stagnated between 2000 and roughly 2012 or so, and even since then has only really risen because a few huge firms pay high salaries. Your average tech-worker still makes an upper-middle class salary that won't even buy a house in the Bay Area, Seattle, New York, or Boston.
All the rampant stupidity on here and elsewhere about how well tech employees are supposedly paid is simple to vanquish: divide by the median home price within a 30 minute commute of the office.
