How much do you have to spend on household help to replace a traditional at-home mom—someone to do the schlepping, cooking, cleaning, child care, and laundry? About $96,261, according to Investopedia.

In all of the voluminous ink that has been spilled on Sheryl Sandberg’s new book, and on women and the barriers they face in cracking the glass ceiling, no one is saying what is glaringly obvious to anyone thinking about how to have a big career and a family: start saving for the army of help you’ll need to pull it off. In other words, a nanny, a housekeeper, and a baby nurse.

This is no longer some bourgeois luxury; it’s a necessity given the lack of affordable child-care options and the reality that men have not picked up much of the slack at home (whether because they are burning the midnight oil at their own work, or because they prefer to watch football with the guys). This is why my husband and I, even though we are currently in the DINK category (double income, no kids), started squirreling away money in a "nanny fund" right after we got married. Why? If I am going to continue “leaning in” to my career, even having a supportive husband is not enough to compensate for this dismal finding: when a husband and wife are both employed full time, the mother does 40 percent more child care and about 30 percent more housework than the father. And in 2013 we are hardly closer as a society than boomers were to universal paid maternity or paternity leave or flexible careers that facilitate the coexistence of career and parenthood. Instead, parents—usually moms—rev up for turboparenting at whatever late hour they get off work. The second shift, as sociologist Arlie Hochschild coined, is alive and kicking.

But not for everyone, necessarily. Many women at the apex of their careers throw money at the problem (to put it bluntly). And this is not a bad thing. It’s the reality of the modern working woman, and it needs to be stated for the record, complete with a financial breakdown of how much it really costs to lean in.

I just did the back-of-the-napkin math, and "leaning in," if you live in a place like New York, San Francisco, or Washington, D.C.—cities that hold golden career opportunities for ambitious women—is expensive.

A full-time nanny costs around $36,868 a year. Then there’s the baby nurse, because if you take only two weeks of maternity leave, as Yahoo CEO Marissa Mayer did, it’s hard to work full time and get up every three hours. That’s $1680 a week ($10,080 for the six weeks). A housekeeper comes in at $25 an hour. At a modest five hours a week, that’s $500 per month ($6,000 per year). Preschool in New York City can cost anywhere between $2,000 and $32,000. And full-time day care is no bargain, clocking in at $24,000.

For some reason, either because women are loath to address the uncomfortable class issues associated with outsourcing a good chunk of their child care, or are ashamed to admit that they don’t change every diaper and wipe every runny nose, we don’t acknowledge a core truth about the women who have gotten ahead. The Sheryl Sandbergs and Melissa Mayers (and even those a few rungs down the ladder) do not only have supportive spouses, nor do they only just “figure it out.” I’m willing to bet that they have backup nannies, drivers, baby nurses, cooks, weekend nannies, housekeepers, and people who come to pack lunches and do the dishes.

Unfortunately Facebook COO Sheryl Sandberg would not come clean in her workplace manifesto about how much help it takes to lean in to her own life and career. (In an interview with Time magazine, she declined to answer questions about her domestic help.)

So let’s put aside the psychological and cultural barriers to women’s success for a moment, and get real: this is equally about the economics. Don’t just lean in, save up (for the hired help).

Ask Carley Roney, 44, co-founder of XO Group, a publicly traded company that is valued at $300 million, and a mother of two boys and a teenage girl. She agrees that child care is the elephant in the room—or shall we say, in the nursery—in the discussion about what holds women back. In reference to Sandberg, Roney says, “It’s easy to say ‘lean in’ when you get to the top so fast, but on the way, how does it work exactly?”

For Roney, who has two sons ages, 4 and 8, and a 15-year-old daughter, her rise to the top would not have been possible, she says, without her mother-in-law who took care of her newborn for free for 10 hours a day—and was on call at all times—when she and her husband, David Liu, launched the wedding site The Knot. “[Without that help] I would never have gotten to where I am,” she says.

These days, Roney has a full-time sitter (55-60 hours per week) who earns in the mid five figures. Her mother-in-law still cooks all the meals and serves as a backup babysitter. “And this is with my kids in school full time,” she says.

Sandberg marshals all the evidence for why the save-up tactic should be at the forefront of every young woman’s mind who has ambitions of, say, making partner, launching her own business, writing a novel, working at a hedge fund, or anything else that takes intense time, energy, or focus. Read: most careers.

Consider this, something Sandberg herself points out in the book: over the past decade, child-care costs have risen twice as fast as the median income for families with children. The cost for two children (say, an infant and a 4-year-old) to go to day care is greater than annual median rent in every state in the country. In New York City, according to the Manhattan Rental Market Report, the average monthly price for a two-bedroom apartment is $4,212; add in a doorman and you are up to $5,782. That alone is far less than the cost of day care; a full-time nanny can cost way more. In the face of these spiraling costs at home, it’s hardly a mystery why many women choose to lean out of modest-earning careers.

If this all sounds elitist, let’s remember that even though Sandberg does her best to get folksy and put on her I-am-every-woman-persona, she isn’t. The dead giveaway is when she recounts an anecdote from her senior year at Harvard about how she forgot to connect the Freudian id to Schopenhauer’s conception of the will on a European intellectual history exam. I’m sorry, this book is a primer for women with impressive pedigrees—the types who apply, and land, jobs at McKinsey, who work in prestigious government jobs, and get plum internships as high school students. This is the breed of women who are fast-tracked for success, but get stymied for a number of reasons, one of which is the cost of child care and the lack of planning for it.

To be sure, even women who can afford all the help in the world opt out. But the point is that whether or not you have high-quality child care—and how much of it you can afford—can make the difference between leaning in and leaning out.

In this country we have all kinds of campaigns that tell us how much we need to save for retirement, but no one is telling my generation, women born in the 1980s, how much it really costs to have the help it takes to launch a high-powered career. They would be doing us a huge public service, however, as Roney has done. Perhaps a “save up” campaign would circumvent the tradeoff that many women face: it’s cheaper to stay home and just do the child care themselves. But if they have been saving for household help since they were 22, that decision might have a different complexion.

I know it does for me.