I agree, I don't expect the kid additions to fully cover the costs. Trying to cover these costs fully is probably unrealistic, as it would lead to a very large salary spread between, say, a founder with 3 kids and one with 0.

The good news is that once you have kids you won't have time for parties or expensive hobbies anyway ... and the joy of having kids makes up for the financial disadvantage several times over. :-))