Scumbag family buys $3,700 ATV but always nickels and dimes me on childcare

I do daycare for a family and they are constantly looking for discounts. Example: they were always forgetting diapers so I offered to buy them for an extra $6 per week. They said only if I provided them a receipt. Wtf. Supposedly your children are your greatest asset, why try to cheap out on the most important service you'll ever receive in your whole life