I think this is normal everywhere in the US. I expect this has little to do with SF and more to do with the fact that many people all over the country, regardless of income level, are living far beyond their means and lack the discipline to make saving a priority; the US average personal savings rate has fallen to 2.5%. But what percentage buys cable tv, smartphones with data plans, auto loans for more car than they needed, etc?
People in the US don't do well at saving. But SF is still abnormal -- you need a considerably higher salary to have the same quality of living + savings in SF as compared to many other cities.
For example: elsewhere in this thread it was stated that a one bedroom apartment runs $2500+ in SF. In my neighborhood, a decent one bedroom apartment might run $700. Sure, you might earn $90k instead of $100k, but you save twice the difference just in rent.
http://research.stlouisfed.org/fred2/data/PSAVERT.txt