> It’s simple. Having a family costs a fuckton of money

I've got two young kids. I wouldn't say day to day expenses are particularly huge.

Sure you can go wild and buy them designer clothes/shoes they grow out of in 6 months, or you can fill every waking moment with white-knuckle entertainment and excitement and that all costs money. But you don't need to do that, the kids don't care what they wear so long as it's got a robot/unicorn/etc on it, and they're often very happy playing with a cardboard box, a small amount of generic Lego, and their imagination.

Food cost is almost a rounding error. Barely anything for an extra loaf of bread, an extra packet of cereal, some more chicken etc. peanuts.

The main cost - beyond needing to live in a larger house which I probably would have got anyway even without kids - is the opportunity cost of having kids: I've probably missed a promotion or two because I've had to say no to work travel, projects, late meetings with the US office etc to go kid related things. That and UK nursery costs are bigger than the mortgage, but again that is "optional" and only for the first few years.

Good luck