That's well above the $8,600.00 national average. Sf residents stand to gain the third most by giving up the car, after Boston ($12,632.00) and New York ($12,589.00) From the press release:
APTA calculates the average cost of taking public transit by determining the average monthly transit pass of local public transit agencies across the country ... APTA then compares the average monthly transit fare to the average cost of driving. The cost of driving is calculated using the 2009 AAA average cost of driving formula ... The savings assume a household gives up one car.