Earlier quoted context omitted.
With that income? Sure, if kids came into the picture during the last day 3-4 years it would increase his expenses, but he’d presumably also have another income, at least for a few years? I don’t disagree that for middle income earners kids are a huge expense, but when you’re making $350,000+ each year, $30,000 for childcare isn’t a dramatic expense. Same with all the incidentals.
The biggest expense is college, at least in the U.S. If you retire before they apply, you may want to be conservative and set aside the cost of the most expensive college. MIT is $77k/year [1]. For two kids, that's $616k. And it increases faster than inflation, estimate 6%/yr. If you have enough money in the bank that you're financially independent, they won't qualify for need based aid, you'll have to pay the sticke…
If I don't have to relocate for job opportunities (currently in Atlanta), I plan to stay here and encourage any future children to stay in-state. That's of course assuming that the state doesn't kill off HOPE by then.