Like many cities that have expensive areas (and Boston/Cambridge certainly do), it's often fairly easy to get to suburbs--some of which have downtown areas--that aren't Midwest cheap but are fairly affordable. I live quite a bit further out but I'm still able to drive in for an evening or take commuter rail in for a day.

I think the fact that it's hard to get out of the expensive areas in the Bay Area in a reasonable amount of time gives a lot of people a false impression of the situation with other expensive cities.