Below is a wonky article about San Francisco startups quickly establishing additional offices in less expensive locales. It appears that San Francisco is the place to seek startup funding, but not the place to run a business.
Even I was surprised by the number of startups who rush to establish offices elsewhere, seeking lower costs. We expect to see that trend as a company matures — even high tech companies — but this study shows many new companies start moving business functions elsewhere as soon as possible, while maintaining a presence in the honey pot for funding — San Francisco.
NOTE: Priceonomics.com is a first class website with interesting insights gleaned from drilling down into data. You would be wise to subscribe to their service — if analyzing numbers is your game.