What does that even mean? People are deciding to have kids because they believe it's too expensive, full stop. What's your counterclaim - they're bad at math and could afford it but think they can't? That if you forced a child on them they could actually suffer through it?
Obviously the truth is that what people say and what people actually do are two different things. In case of having children we actually have proof for that!
> That if you forced a child on them they could actually suffer through it?
Absolutely, that’s how it always worked before we’ve had good contraception .
Generally speaking countries that have tried to do something about their abysmal birth rates (Hungary, Czechia, etc) by putting in substantial economic incentives (i.e. 4 years of maternity, free accomodation, etc), have found that it moved the needle very little and certainly there can't be much talk of reversing the trend.
Also, I believe that our culture of over-parenting (and therefore many of the associated costs) is a _consequence_ of having fewer children, not the cause. If you put all your reproductive eggs in one basket, you are motivated to overprotect them. That makes a culture of (at least from a historical perspective) insane parenting demands that simply don't scale.