I turned down an internship in Palo Alto because the least expensive temporary (< 12 mo) housing I could find in the Bay area was a bunk in a "hacker shack" for ~$1k/month. The mortgage on my 4/2 house in Mississippi was <$500/mo. The person who offered me the job laughed when I told her about the wild discrepancy in costs of living and said several potential interns and employees over the years backed out for the same reasons.