Any reason to think their baseline is making money? The arithmetic of daycare - market-minimum hourly pay for the workers, vs. legal minimum per-child staffing levels, vs. tight parental budgets - is damned ruthless.
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.