In a city that attracts some of the most successful people in the WORLD, R.E. prices will be high; its a fact of capitalism. For the rest of us, SF could look to Singapore who has the same problem 5Xfold. What they've done is create a government-owned housing system that works under the free-market system, but down-shifted the price points to match the incomes of the average Singaporean.
From what i've seen, it think their model is the best way to preserve capitalism and people's dignity without becoming a socialist state.
Most of us live in San Francisco to take part in the city. If we wanted a big cheap place to live we would be in Texas. Allowing developers to build higher density, smaller residences, near mass transit gives everyone at all income levels more affordable options. With no cost to taxpayers!
Here's a great article about Affordable Housing By Design from our own San Francisco Planning and Urban Research Center
Paid for by Phil Ting for Assembly 2012. FPPC ID# 1343137