Is this really true about cost of having a child?

That seems...excessive. I mean my one lives in primark or sainsburys stuff, a decent pair of clarks shoes. Days out he had more fun running in a field and being free that dragged around a zoo. But it's all relative isn't it? The initial set up can be pricey; I wouldn't buy a car seat second hand so when I bought new I got a travel doodad that was pram and car seat.
Childcare costs however are pretty expensive. But my husband and I have managed on 40k income combined and he is a fairly polite (had his moments) small boy. I did manage to get several clothes bundles of different age ranges on fb market and plenty of books from charity shops. But I'd say your real costs will be childcare.

I hope you’ve factored in the cost of soft fruit. I barely bought any before DD was born, now it’s major chunk of the household budget.

It depends on your kids to some extent and if they have hobbies or attend clubs. I find school more expensive than nursery was though. If your husband earns less than 30k I think you’d absolutely be skint if you went part time.

We aren’t on high wages, and we’ve never saved as extensively as that. If your DH is on low wages and you aren’t a high earner/go part time you’d probably have been eligible for the childcare element of universal credit, which we claim as nursery is over £600pcm for just 2 days, wraparound for middle child is £15 per day. We also claimed UC top up when I went down to SMP.
I think there’s an element of only spending what you have, I sourced a lot of things very cheaply, I buy a lot second hand and I sell everything on as soon as we’re done with it to fund the next stage.
things like swimming lessons are expensive, but whilst my kids are swimming they don’t do any other extra curriculars, once they can swim they can pick a different club to do.

Our 2 are now teenagers and this is definitely the most expensive stage for us. Childcare costs a lot more now than when we were using it though so it may be different for those whose kids are younger now.

Saying that, costs were much more predictable when they were preschool and primary aged.

£600 for the child per month?
once ours started school I think it was far less than that, but everyone will be different.

here we pay £35 per child per week for after school club. Holiday club is £15 per day but we use our leave for some of that.

clothes we gets loads of hand me downs, charity shop bargains and sale stuff. I very rarely buy much full price.

days out we mostly do cheap or free stuff - beach, moors, park etc.

food we buy a lot more fruit and snacks but meals isn’t much more as it’s just making a slightly bigger portion than for 2 of us.