Average monthly car payment for a new car in California is $738 ($532 used). A record share of Americans are payment $1000 or more on monthly car payments. [1]
Average monthly parking in SF is $340 according to SpotHero, if you have your own place and spot, that added $80-100,000 to the price of your home, so you can decide how you'd like to value that. Today 7.5% APR mortgage, that would add $7500 per year in interest, $625/month. Less if your mortgage is lower-interest.
Bankrate says the average annual insurance cost in SF is $2692 ($224 per month).
AAA says the average price of routine maintenance is 10c/mile. Average distance traveled is 14000mi/yr, so that's $1400/yr ($116 per month).
Add in gas, tolls, fines, registration, collision damage, etc.
Should be $800-1000 per month on top of your car payment.
Which is incidentally what AAA found. US average is $894 per month on top of the purchase price, or just shy of $11,000 per year. And one has to imagine it's a lot more than that in San Francisco. [2]
The GGP's $1K per month estimate is actually probably about half of what people pay all-in amortized over the ownership period of a car. 6.6% return is below the S&P average. I dunno man, the numbers check out, and may even be quite conservative.
