$200 to $250 per sqft. in this market is a bit low for San Francisco. I'd be more comfortable with a $250 to $300.00 level, if you have special features, you may way to kick it up to $350 to $400. Keep in mind that in the event of an earthquake that caused substantial damage to the city, construction costs would sky rocket, as there would be lack of construction workers, and materials. I don't recommend over-insuring and paying a needlessly high premium, but the worst situation you can be in, is finding yourself underinsured after a catastrophic loss.
I certainly hope that never happens.
CA Real Estate Broker