Have returned from a nine day trip. The ParkSFO cost using a stay nine days get four free no sales tax included coupon was 17.95 x ((9 - 4) + 9 x .15) = $113.98; self-park rate, but got valet because of packed lot for spring break. In comparison, Park n Fly valet using Costco vouchers would have been 10 x 9 = $90. I am preserving the few vouchers I still have for another trip.