Take a look at Outer Mission, which has a monthly rent of $2150 and an affordability of 4.0.
10.24 $/hour * 8 h/workday * 21 wd/month = 1720 $/m
4.0 * 1720 $/month = 6881 $/month
6881 \approx 3 * 2150
So while having 4 incomes is recommended for living there, it isn't actually needed. You could live there on a smaller income by being careful about your smaller expenses.