I don't think what you've written is exactly true. At least some of the rental property in San Francisco is rent controlled (possibly a lot of it if you believe this site: http://www.sftu.org/rentcontrol.html). If a person/family lives in a rent controlled unit, rent increases aren't necessarily tied to the rental market, but rather are limited to a percentage of the CPI (1.9% increase for the current year - http://www.sfrb.org/index.aspx?page=1501). Wealthy neighbors don't have much to do with it in these cases.