Sounds like a relative newcomer to the Bay Area. Newcomers are, generally speaking, always a bit disconnected, and tend to have odd ideas about the area they've moved into. Over time, I'd expect that poster to get a better view of what San Fran really is. As you said, "prosperity disparity", "income inequality", whatever you want to call it, is a good deal worse in San Fran than it is anywhere in the rust belt. That's for sure.
Unskilled laborers moving to SF thinking it's the land of opportunity are likely to be disagreeably surprised.
You are 100% disconnected if you think this is true. The wage gap is an even bigger issue in SF than Cincinnati.