The Pew Research center conducted a study to see how income classes have changed over time in 229 US metros. Part of the study was highlighting the 10 metros with the largest percentage of upper-income populations. "Upper income" was defined by being more than double the US median household income relative to the national average cost of living. That means that very expensive areas are adjusted downward. Despite this, the San Jose metro can in 4th on the list, with 31% of the population considered upper class and a median household income of $187,390. San Francisco was 9th on the list with 28% of residents considered upper class and a median income of $185,290.
However, I would argue that if you have a household income of $187,390 in Silicon Valley, you are not wealthy and most likely in the upper middle-class bracket based on purchasing power. Likely you are not living in an extravagant house or enjoying a lavish lifestyle. If you have kids and a mortgage, you might barely be getting by. Check out the source link below for the top 10 list and more details.
Source: Business Insider, hat tip to Barclay Livker for sending this in!