On top of that you get a bunch of other subsidies - e.g. in Norway again, nursery spaces are guaranteed by law and capped at around the $200/month mark, and child support is paid monthly until the child turns 18 at about the same rate.
Norway is below replacement, so we know that rate is too low.
Maybe your 60k/year on an ongoing basis would be sufficient. Whether anyone would be prepared to take the economic hit of trying is another question.
I suspect we'll see a lot of desperate flailing, creeping authoritarianism (e.g. curtailing abortions etc.), virtue signalling (it's your patriotic duty...), and increased reliance on immigration (until that supply also dries for an increasing number of countries) before someone is willing to try to figure out what a high enough number to change it is.