Most parents I know tend to inflate the cost of the kid by virtue of overspending on things. Have to buy all equipment new. Have to buy the best tyres for the car because there is a 0.00000001% chance they might be in an accident and that tread makes all the difference. Shit like that.
The other good one is education, where they absolutely have to send the kid to private schooling.
Don't get me wrong, I agree education is important - but I wouldn't cop for them to go to a private school. I would cop for private tuition on top of their public schooling. I remember that being extremely effective with me.
Using your logic, what is effective for you is effective for all others. Life doesn't work like that.
Since most people I know don't keep a record of every penny they spend on their kids, I'm not clear how the aforementioned child raising figures were concluded. My suspicion is that they are a generalization reached by calculating the average various expenses of child rearing. Whether extraneous costs were included in the final figure, is unknown. May I suggest that more affluent parents most likely spend more on their children than the less affluent parents.
If the parents have four children to raise, based on the amount given for one child, they will spend close to $1,000,000 on their children, not accounting for inflation. This might help explain why the birth rate is dropping.
Private school isn't always expensive. Kids in parochial schools are sometimes awarded scholarships which cover all or part of the tuition. Folks who think they are buying more expensive tires for the safety of their children are most likely lying to themselves and others.