But I don't really disagree with the broader point. In addition to being the center for at least a certain segment of the tech industry, it has progressive attitudes that are important for many, has what perhaps most would consider one of the best climates in the country, and has easy access to some of the best recreational opportunities in the country.
Detroit may have significantly cheaper housing but it's going to be a tough sell for a lot of Californians--and therefore for companies that want at least a local core of tech talent--i.e. not 100% distributed. [ADDED: Although as the other comment says, very generous salaries relative to the local norms may not convince everyone to move, but they'll sure convince some.]