You can live as comfortably as you want (I do) but the catch is that you'll probably have to be without children. Anecdotally, everyone I know with families tends to move outside of SF because for the price of a 2 br apartment, you can get a mortgage on a nice house.

There are affordable areas to live ($800-$1200 / br) but you'll have to be quite patient in your search and be open about where you'd like to live.