This is true to some extent and costs can be reduced, but if there's more people it's going to require more space than before. As a single person for example someone can live in a 400-500 sqft studio apartment, but that becomes difficult with adding more people in. People may not want to give a potential child a lower quality environment, and thus it's a logical choice to not have children due to financial or space reasons.
I just disagree, and that's fine.
You can't put a number on having a kid.
Yes, there can be an average, but this average can be worked around.
If you are poor and cannot afford $250k, cut corners.
I'm sure that there are plenty of ways to save, there's not one answer on how much a kid can be.