It's honestly not a question of objective or absolute material wealth, it's subjective and relational. Like marx himself pointed out that social reproduction is based on a basket of goods that is culturally conditioned. It's why young white people today can objectively have a better material standard if living than their ancestors 100 years ago and still feel poorer, because effectively they are. If your cultural context says you need 10 wealth to reproduce successfully and safely but you only have 8, it doesn't matter that your grandparents had 7 social wealth with 6 kids because for them successfully reproduction only required 4.

Additionally the perceived rate of change in that wealth is if critical importance. If you have 10 wealth and that is what society has conditioned you to believe is required for reproduction, but you believe that in 10 years you will have 9 and it will still require 10 you will avoid reproduction.

There is this bizarre belief that humans just reproduce willy nilly and always have. That our ancestors were just morons who didn't know where babies comfrom. When the truth is they knew, and especially women, had elaborate methods of controling their reproduction. The difference between us and our ancestors us the effectiveness of our tools for controlling reproduction, not that we didn't understand it and try to control it.