Uh..........no...........unless you never let them do sports, take dance lessons, etc.........
I made that statement very tongue in cheek of course!
But let's just say that different parents have different opinions of what constitutes "things they have to pay for".
And for those things that you do pay for, there are the $50 versions and the $500 versions (dance classes, sports teams, summer camps, swimming lessons/pool memberships).
We get close to $2000 in tax savings per kid. That goes a long way toward our kid expenses. I have never split out kid-related expenses separately from our other household expenses (is it even possible?), but the kid related tax savings represent about 17% of our basic expenses. And a majority of our expenses are fixed (ie wouldn't change significantly due to changes in household size).
And due to some social welfare programs being tied to household size, sometimes having more kids qualifies you for certain programs you otherwise wouldn't qualify for. Not currently benefiting us, but this will probably work to our financial advantage during FIRE or semi-FIRE or if DW or I cuts back hours etc.
Beyond that, there are changes in lifestyle I have noticed since we had kids. Less dining out for a number of reasons. Less free time to need to fill with expensive pastimes. Many kid-oriented activities are free or cheap Off the cuff: playing outside, playing with friends, parent groups, school activities, museums, zoos, fireworks displays, riding bikes, playing at playground/parks, hiking, nature walks, libraries, reading, learning, internet games, watching tv/movies, swimming. And that was just this past weekend!
Philosophically, I think some of the best things you can do for your kids don't cost anything other than your time and attention.
Take note our kids are still young (both will be in elementary school this fall), and so I could be in for a very rude awakening (and I have budgeted for this to a certain degree). But we also live in a moderate income area ("gentrifying area") so our kids don't see lots of spoiled rich kids surrounding them all day (another benefit of living in a moderate cost neighborhood and going to schools with a high proportion of low income students).