Ask Mary Adams if she was stricken with “empty nest” feelings after her two sons moved out and she shrugs off the question. After all, the Northern California native says, her boys never strayed far from home after high school, and both worked at one time or another for the family’s thriving pool-maintenance business. But listen a little more closely, and her tale of life after child rearing may sound all too familiar.

For Mary and her husband, Rick, the empty-nesting phase began with a few splurges aimed at getting them away from their suburban hustle and bustle. First, they bought a 35-foot RV for tooling around the Golden State on weekends, with their Jeep in tow. A couple of years later, they found a little five-acre ranch getaway not far from Napa Valley. And like a lot of empty nesters, they eventually brought some four-legged “children” into their lives. Only these weren’t run-of-the-mill rescue tabbies or finely bred pedigreed pups. The two creatures Mary and Rick bought on an impulse weighed around 250 pounds each, had lanky necks, two-toed feet — and alluringly long eyelashes. Today the couple’s llama herd numbers more than 50, and Mary says they’ve spent upwards of $500,000 living la vida llama: buying animals, breeding them and showing them competitively at every opportunity. Asked whether raising llamas might ultimately be even more expensive than raising kids, she does the mental math. “Given how many we’ve got,” says the self-described llamaholic, “probably — yes.”

Wait a minute, parents are saying: Can there be anything more expensive than raising kids? The way most Americans figure it, by the time they finally reach their empty-nest years, they’ve gotten over life’s biggest spending hump. After all, the government (conservatively) estimates that for an upper-income family, the cost of raising a single child from birth to age 18 will run about $377,000 — and that’s before the little matter of college tuition. Once the kids have gone, parents often experience (in addition to those well-documented feelings of loss) an exhilarating sense of financial freedom: No more bills for braces and tennis lessons. No extra mouths to feed. No need for the large house and the large mortgage that comes with it. And of course, no six-figure tuition to spend years saving up for and then shelling out. Only it turns out that, at least according to the most recent evidence, when kids go out the door, many parents discover that their days of spending have just begun.