Wow...that would be $17 Canadian for parking if I was visiting the zoo on a Saturday or Sunday. According to the zoo's website there is also valet parking on weekends and holidays for $25 U.S. ($33 Canadian) and admission is now $23 U.S. ($30 Canadian) as well. I know that San Francisco Zoo has gradually, step-by-step, showed signs of improvement over the past decade, but those fees are truly outrageous. At the end of the day it's still perhaps a 5-hour visit for a zoo nerd at best.
San Francisco (the city as a whole) is indeed expensive. I stayed downtown that night and had to pay thirty bucks extra to my hotel for parking (and it was a horrendously tight parking garage). Thankfully breakfast was included. When I went at the beginning of summer and stayed in Chinatown I had to walk to a French Bistro just across the entrance to Chinatown and paid (with tax and tip) thirty bucks for breakfast - the most I have spent on breakfast in my life.