The cost of living difference between Minneapolis and San Francisco is HUGE. For the cost of an apartment in San Francisco you could have a huge house on 1/2 an acre of land in the Minneapolis area.
If you are single or DINK (dual-income-no-kids) and don't really need more than one-bedroom apartment - you would probably be better off living in Bay Area and working for Google (or whatever). That way you would be able to accumulate cash faster or travel internationally a lot more.
With kids - it's better live in a provincial suburb, have big house with nice backyard while working for 30% smaller salary.
This calculator takes into account more, like housing, food etc: http://www.bestplaces.net/col/?salary=107798%20&city1=50...
"A salary of $107,798 in San Francisco, California could decrease to $56,716 in Minneapolis, Minnesota"
Which is much more in line with my personal experience having worked in both Silicon Valley and Minneapolis.
If you're a good engineer, it is not uncommon to pull down 107k or more in Minneapolis as well.