I can buy 1-3 boxes of formula milk in an hour of breastfeeding so how is that?

I work m-f 10 hour shifts and I have 7 kids and I still pump at work and breastfeed at home. Haven't had to buy a drop of formula. My little is 5 mo old and my other kids are 3, 5, 7, 15, 17, and 21. I think it really just depends on the person and what they can handle with their lifestyle. Breastfeeding/pumping isn't for everyone and a fed baby is a happy baby. I formula fed my 1st but my other 6 never had formula. You literally cannot tell a difference in my oldest vs the rest of my kids.