Housing in Boston is substantially cheaper than Silicon Valley.

Anecdotally, when I moved from Silicon Valley to Boston, my rent stayed the same price and but I got to live in twice as big a house.

Non-anecdotally, look at these real estate price maps.

Boston (Middlesex County, north side of the city): http://www.trulia.com/home_prices/Massachusetts/Middlesex_Co...

SF (San Mateo County, south of SF): http://www.trulia.com/home_prices/California/San_Mateo_Count...

You can buy a relatively large house within a few miles of downtown Boston for around $400k. I don't think that's possible in SF.