1 kid, 5 months old. Costs have been relatively low. $130 per month for health insurance - low deductible. Maybe $100 for everything else for the baby. Healthy baby. The utilities are a little higher. Gas for hot water is $5-10 more per month. Electricity, maybe the same. We use a little more water too. We already had a 4 bedroom house, so housing was not an "additional" cost for us. All together, around $250 extra allocable to the baby.
I don't buy much of the typical "baby junk" that people seem to need tons of. We've received tons of gifts of clothing, and have not bought a single article of clothing.
Startup costs were $500 or so including health care, baby stuff, etc.
Considering the tax savings are around $150/month, we really aren't spending that much money.
We also spend less each month now. Dining out has decreased significantly (perhaps 60% less than pre-baby). We don't spend as much on discretionary purchases (toys) because we don't have the time or energy to go shopping. I also feel motivated to curb spending, because I know I have another mouth to feed and support. Factoring in our reduced spending and the tax savings, our child may not cost us anything currently.
When she starts eating more food and requiring purchased clothes and toys, I'm sure costs will increase. College costs should be relatively pain-free, assuming the state schools here are as reasonably priced in 2022 as they are now. A wedding - well, she's going to be old enough to pay for it herself!
The benefits are unquantifiable. At this point, I can't resist posting a picture of our daughter. It was taken on April 15 of this year.