I would agree that a lot depends on your lifestyle, but make no mistake about it, kids are expensive. I don't know about this $250K thing, but I have had my own experience to draw from. Aside from the cost of college, you assume that everyone lives in a good public school district. If you don't (and many do not) there are added costs for private school. And even still, preschool is not free. Starting in the fall, I'll be paying $320 a month for my youngest daughter to go to preschool. We do live in a good school district, so elementary school and beyond are "free" for us, but there are added costs there too. The cost to register alone is $215. I just paid for my 2nd grader's 2013/2014 year. Our school also charges an extra $250 for bus service. I choose to drive my girls to school, but not everyone can do that. During the school year there are field trips, teacher gifts, book fairs, birthday parties. None of that is free. Plus once they get into middle school, there's the cost of text books, the cost of extracurriculars, etc. We've been warned by parents in our neighborhood with teens that the cost of the public highschool is over $800 just to sign up and get your books. Yikes! So much for "free" high school. BTW, once they start driving, get ready for the added cost to insure them on your insurance plan. Teenage drivers are not cheap to insure that's for sure! Speaking of insurance, there's also life insurance. Right now my husband and I are paying $300 a month for life insurance on both of us. This is only because we have children. Believe me, if it were just my husband and I, we would not bother with this type of insurance. If one of us died, the other could easily handle ourselves financially. With kids, that's a different story. They need to be protected and financially secure, so life insurance is in order.
If your friends both work, then who will take care of baby when it arrives? You say your friend will keep working when baby comes. Well unless they have family in the area willing to be the daycare for free, then they will have to pay for a nanny or daycare - very expensive. This is tens of thousands of dollars a year. You can take that right off their current bottom line.
You may not notice some other costs creeping in but they are there. I have 2 kids and I drive them to a lot of places. That is extra gas expense, which right now ain't cheap either. Food, yes, especially if we ever decide to dine out with the girls. That's 2 extra people we're paying for to eat. Also bigger ticket stuff - travel, that's 2 added plane tickets. We went to Puerto Rico for spring break and it cost us an extra $1,000 just for the two children to fly, let alone souveniers, food, etc. on the trip. Before kids, that $$ would have paid for an added weekend trip for us alone. Again, this is a lifestyle choice I know and not everyone will spend money on vacations. But if you are a person who likes to travel (and we are) you need to consider that in your cost of living. My husband and I used to travel frequently before kids. Now we can only afford one trip a year and sometimes those are not even doable. This year was a good year.
If you ever like to go out to dinner alone, again a lifestyle choice, but now it will cost you $50 just to get out the door because you need a babysitter.
I honestly could go on. But in short, think about everything you spend on yourself to live and multiply that out for every extra person you add to your family. Doctor visits? Co-pay per person. If they need medicine, there's that too. Milk? Now has to serve 4 people (for us) not just 2. Clothing? There's only so many hand-me-downs to get you by. Shoes? Ugh, their feet grow out of shoes sometimes faster than I can buy them. School? It's never "free". How about furniture? The children have to sleep somewhere. Even if your friend can get a used crib from another friend, what happens when they're ready for a big bed? And a mattress? And linens? Ok, I have to stop myself or I will turn this reply into a gothic novel.
Bottom line, you are way underestimating the cost of having children. Maybe your babies are still super little and you are not thinking about them as they grow into people. If that's the case, I am afraid you are in for a rude awakening my friend...because they only cost more money the older that they get.