It's most expensive to have 1 child - then each child after the first is cheaper to raise, especially if they are of similar age. Once you get to 3+ kids it almost makes no difference. But, it depends very heavily on your lifestyle. If you think that every child needs their own bedroom, they all have to go to private schools, they all have to go to Disneyland every year, if you have to pay for healthcare and/or kindergarten, then yeah, the costs are exponential. But if you live in any modern country with good social care(this does not include US) and you think kids can survive without luxuries, then yeah, it's actually completely doable.