Yes, everyone’s net pay has to cover rent/mortgage and childcare, the difference being that the vast majority of people don’t have £6k a month before those bills.
We would have to have jobs paying £65k a year to get £4k a month. She’s actually getting £6k due to CMS and her £14k a year job. Which is a gross annual salary of £110k, by which point we would have lost any allowance for tax free childcare discounts so wouldn’t even get that 20% reduction.
Add in other benefits and discounts like free school dinners, reduced entry fees for attractions, NHS dental and optician support etc on top of that too.