Unless it's some "Mrs. Smith's In-home Childcare" deal, it ain't a carer staying late at $2/minute - it's randomly keeping a business open, at $120/hour. With (good bet) a mandated-minimum staff of 2+. At SF wages. Plus the extra staff churn that randomly having to stay late causes.

Parents wanting ever-so-forgiving cheap daycare need to move an idle grandma into town.