Park 'n Fly has a throwback rate (today only) on their social media sites for parking thru 12/20. Comes out to $10++/day at SFO, including valet. They add some junk fees, so it's a bit more than that. I got 3 days for $39 ($13/day), which is not too bad for valet. https://www.facebook.com/parknfly/