This is a very interesting question. I recently read that the cost of raising a child from birth to age 17 was almost $225,000, for a middle class family earning less than $100,000 a year. The cost per child goes down if you have more than one.
I just did some quick calculations and was able to come up with $155,000 (updated from $105,000, orginal only included one year of day care, not 10) considering I only spent 10 minutes, I'm sure I forgot a lot of things. My children also do not play sports (tried soccer and softball for 2 years when they were younger). We haven't had any major medical expenses, the usual doctor co-pays and medicines, luckily my health insurance covers glasses, and luckily no braces.
I think there are so many factors that you could add into this that make your cost to up or down significantly.
For example in my case some of the things that are low cost for me,
no sports
no major medical costs, I have a great health insurance plan at work
low food costs - we don't eat out much and keep grocery bills down (have you ever seen how much a teenage boy can eat? some families spend a lot on food)
our school district includes free preschool
my girls play musical instruments - I rent them through the school @$50 a year - my friend in a nearby town pays $50 a month (elementary school)
clothing - my daughter gets a lot of great hand me downs from her cousin and when they were little, yard sales and consignment shops
no video games in my house, so we haven't had the huge costs of the gaming systems and all the games , let's not talk about the cost of books)
my girls do girl scouts, which overall isn't a very expensive activity, at least for their troops
Our the other hand since both of us worked, we paid for daycare at a cost of $5,600 a year per child, and this was reduced because family helped out a lot and our (hubby and I) work schedules were different so many times he was home with the kids while I was working and I was home when he was working.
Don't even get me started on all the costs of fundraising, of course you don't have to participate in everything, but between the selling, book fairs, car washes, dinners, auctions, etc, it all adds up.
Teens don't need cell phones. But in my case the cost (about $200 a year for the phone and service) is well worth it, so I can reach them, they can reach me, and it's a safety line.
As mentioned, my girls play instruments. By 7th grade, when we (parents, child, and teacher) knew they would continue with music, we had to purchase instruments, they require special shoes for marching, and they took a few lessons. And they also play with groups outside of school, so there's the transportation cost of driving to practices and the cost of attending the concerts. And did I mention the $650, I just paid for her to go to a band competition with school. (Not complaing - It's great! Most of their friends are in band and they're a great group of kids - still costs a lot less than most sports).
When they reach high school it's the constant, I need $5 or $10, to go to a school sports event, the movies, so and so invited me to go here or there with their family....
The figure above doesn't include the cost of driver's ed and car insurance, I'm just ignoring that for now...
As the commericial says the cost of housing, cloths, food, activities $225,000....
the love, the laughter, the smiles PRICELESS!