BLS (which is what most employers use as supporting wage data. Some employers provide their own sources which is a whole other can of worms) allows you to search by "metropolitan statistical area."

http://www.flcdatacenter.com/faq.aspx

For instance a level 1 "programmer" in SF makes about 70k. A level 4 "Software Developers, Systems Software" makes about 158k...

My point is that the argument that h1b employers must and therefore do pay the prevailing wage is incomplete with out knowing the employees skills and the wage data the employer chose to set as the prevailing wage.