$69,000/year is not "below poverty level" in the Bay Area. I mean, maybe some random charity has a very idiosyncratic view of what they personally view as "poverty," but it's not below the poverty line in any official sense, and, practically speaking, a $69,000/year wage makes you much richer in terms of purchasing power in the Bay Area than $11,000/year (ie, below the actual poverty line) in rural Alabama.

I kind of think the high cost of living thing is not that relevant here. The cost of living is high because the people who live there make a lot of money. If they made more money the Valley wouldn't be more affordable for them. It would just be more expensive.

There are many other factors that influence cost of living in a given area, not just income.

Plus, in some cases increases in income lags behind increases in cost of living.

Not everyone in the bay area makes a lot of money. There are a lot of blue collar/service workers who don't even know what hackernews is who would kill to make that 70k a year.

Correct but they have nothing to do with the conversation we're having.