That said, having kids above repopulation rate might not just be about making things affordable. If people don't have a strong reason to have more than two kids, and if kids don't have tactical value like they did when they contributed to the family business (e.g. did farm labor, helped around a household, provided old-age care), then it can be difficult to justify having more than two even if raising kids is totally cost neutral (simply because it's more complicated to have a larger family—more of a logistical and mental burden).
"I can't afford kids" is an excuse used by people who don't want kids but are unable to admit that. You can't actually afford kids if they would be under a real risk of starvation - which is a real risk in North Korea, not any Western country.
Don't read me wrong, I'm not saying here having kids is an obligation.
If you want to make kids cheap, you have to reduce the competition for resources, or increase resource abundance.
Neither one is particularly achievable through bureaucratic policy.