Who are the Rich?

I guess it's settled. The IRS is changing its auditing policies away from the "kinder, gentler IRS" of the recent past and is stepping up audits on the rich, the self employed, and those who have their taxed prepared by unscrupulous tax prep services.

The Rich, as defined by the IRS are those that make over $100,000 per year. So, in the Bay Area, that pretty much means everyone. In many of the suburban communities on the Penninsula and in the Southbay, the average household income is $210,000, with both parents working.

I'm curious as to how incomes here got so high. Because of the critical mass of big money high tech companies vying for talent? Could it be that merchants know there are big money tech companies with money to burn, so they simply raised the cost of everything, knowning the companies would pay higher salaries? Probably some sort of combination between these, and many other factors.