4 kids, typical tech salary ladder career / upper middle class lifestyle, my marginal costs are maaaaybe another $40k year in total ... and I get about a $25k tax break for having them.
And houses today are also probably a lot bigger than they need to be; often justified as a requirement for families. I don't think it's really necessary, but I seem to be an outlier with my 950 square foot house.
I imagine you've made more pragmatic choices, but I think there is also an element of luck; a lot of people get bankrupted by medical needs, and each kid is a reverse lottery ticket there. Speaking as someone who was once a kid with a lot of medical needs that didn't always get addressed, I can tell you that that does happen sometimes. And I needed to go to school; with my medical issues, the trades or military or whatever was never an option, so someone had to pay for that.
I guess all I can say is "shit's tough"; sometimes you get lucky, but I never seem to.