Having a wife at home also could help lower costs since their entire job is to efficiently and cost effectively run the household, acting as a sort of domestic accountant. Over time she'll learn the best products to buy for the price, the most cost effective nutritious food, how to handle various household activities effectively (efficient clothes/dish washing by reducing cycles), among various other matters that can either lower costs or increase utility.

also, child care is insanely expensive, for lots of families it can basically take up all the cost that the second parent would expect to bring in.

+1 If your kids are old enough to be in school, that's one thing. But if your kids younger than 4 or 5, paying for daycare during normal work hours is expensive! Easily over $1,000 a month.

However it can become a liability if you separate (alimony). Everyone thinks they won't, but it's worth checking the stats.

I would argue the liability is on both sides, not just on the person who pays alimony. Society has exceptionally little ways to welcome stay at home parents back into the workforce. If a stay at home parent's spouse is disabled or killed in an accident (unfortunately common in car-centric societies) the entire family is now in serious, serious trouble.

"common" seems erroneously high there. For any given household with a stay at home parent, the working parent's lifetime risk of dying in a car accident is less than 1 in 100. The risk that they'll do it in the years working to provide for the household is likely less than 1 in 200. Meanwhile, the risk to divorce is around 2 orders of magnitude higher. (I'd agree that "divorce is common"; something that happens about 1% as often, I don't think of is common.)

If you're making relationship decisions based on statistical chances of separation you're already operating on a level of fundamental distrust. If you're planning an "out" in what ought to be a lifelong relationship then you're already not in it for the long run. Risk is part of what makes a marriage meaningful, you're mutually accepting that risk and embracing it for the good of the other.

The biggest cost is the childcare

> Makes me think that in a lot of ways saving money is really tax efficient compared to slogging for more ordinary income.

It depends on how similar your wife's income would be to the cost of childcare really, which also depends on how many kids you have, etc. Also, what happens when your kid's don't need childcare? There's some huge(maybe) opportunity costs to account for from putting her career on hold.

Working moms (parents) can do most of the other stuff with a job so it's not really "savings". My wife does anyways. Only extra we spend is a couple hundred a month for biweekly housekeeper so we don't have to do the deep/detail stuff. I take care of all the house stuff and finances and spend roughly the same on outsourcing lawncare. It's not worth my time and effort compared to the cost and never ending hassle (I'm in Texas and it's 110F outside and grass grows 9-10 months out of the year)

My spouse was a sw engineer who became ft stay at home parent shortly after our second child. Yes it's not how much you make but how much you can save after that counts. Certainly she saved us a lot of money. In my case the intangible benefit of never worrying about my kids cannot be overstated. I really think it made a huge difference. I live in a community property state and I feel sorry for stay at home spouses who don't have this safety net. For the most part I think they deserve it.