Developed countries typically have lower birth rates than undeveloped countries.
That is more to do with education and women's liberation (including contraception), than finances. Which I suspect is still the predominant reason that birth rates are dropping, with finances just a secondary reason.
They lack a social safety net for retirees, so children take care of them in their old age. Children are also a source of wage labor. We're already softening up on child labor here in the USA to address the labor "shortage".
Seems like a side effect of unchecked greed instead. If it were properly designed people would be able to afford enough bread and circuses to stay complacent