It's the kind of calculation that ruffles the robes of administrators at the most prestigious universities in the country. It's a blunt bottom-line approach to a postsecondary education, a show-me-the-money college survey. And it's one academic contest that the Ivies don't win.

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For decades, the best-known college rankings have tried to encompass everything from alumni giving and "academic reputation" to dorm amenities. But a few years ago, SmartMoney stripped all that away in favor of a simpler benchmark. With help from PayScale, a Seattle-based compensation-data company that maintains salary profiles of 29 million workers, we collected median pay figures for two pools of each school's alums: recent grads (who've been out of school for an average of two years) and midcareer types (an average of 15 years out). For each class, we divided the median alumnus salary by tuition and fees (assuming they paid full price at then-current rates), averaged the results and, finally, converted that result to a percentage figure. The outcome: a measure of return on (tuition) investment that we've dubbed the Payback Score. For example, a hypothetical grad who spent $100,000 to attend college and now earns $150,000 a year would score 150. The higher the score, obviously, the better.

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It's admittedly an imperfect bit of math. It doesn't take into account financial aid, at a time when schools say they're increasing it. Nor does it include a host of intangible factors that can make any education more valuable. But a growing number of parents and applicants are giving such calculus more weight, in the face of the steady, recession-proof rise in college costs: Private tuition has increased 70 percent since 2001, to an average of more than $27,000 annually, according to the College Board; public tuition more than doubled over the same stretch. What's worse, a weak job market has made it harder for grads to pay off student loans. Steven Roy Goodman, a college admissions consultant in Washington, D.C., says even the most prestigious schools have more questions to answer about their alumni incomes. "You have to look at the yield from your education," he says. "Not everybody who goes to Columbia becomes a multimillionaire."

Maybe not, but the average Columbia grad can expect to earn $100,000 a year by her mid-30s, according to PayScale -- 2 percent more than a graduate of a top-priced public university at the same stage of life. So does that justify the extra 50 grand that he or she might pay for an Ivy League education, NYC-style? You decide. To help in the process, we used our pragmatic dollars-and-cents metric to examine 50 schools at the highest end of the cost spectrum: the eight Ivies, plus more than 40 of the most expensive non-Ivy private schools and public universities (based on what they charge out-of-state students). We then determined an overall payback ranking as well as a ranking by category. Here, the full transcript on America's best and worst college deals.

The Ivy League

Avg. payback score: 94
Avg. salary for recent grads: $55,463
Avg. salary for midcareer grads: $112,838

In any discussion of college expenses, the gold-plated cost of an Ivy League degree quickly becomes Topic A. Among this elite sisterhood of schools, four years of full-price tuition and fees for the class of 2009 averaged just under $138,000 -- 82 percent more than what members of the class of 1996 paid. In response to this soaring bill, many of the schools have dramatically boosted financial-aid packages -- tapping endowment money for grants in order to keep families (even modestly affluent ones) from having to borrow heavily to pay for college. Princeton, the top-finishing Ivy in our survey, was the first one to pledge to give grants, rather than loans, to all students qualifying for financial aid. At least 60 percent of Princeton students in the class of 2014 are receiving scholarships and other aid directly from the school, totaling around $40,000 a student. Harvard says the same is true for its incoming freshmen.

That kind of largesse certainly will make life easier for aspiring Yale grad David Marcano, a valedictorian and Eagle Scout from Worcester, Mass., who will be paying less than a tenth of the school's sticker price of $56,000 for annual tuition, room and board. "I told David, when he gets rich, he needs to do the same for other kids," says his mother, Ramona Gil. And certainly, if PayScale's numbers for future grads are any indication, his future income won't be hurt by his academic pedigree: Ivy grads, on average, outearn their peers from the get-go, and the earnings gap between them and top-tier public-school graduates widens over time, from about 14 percent right after graduation to 26 percent by the time they're in their 30s.

Still, critics say the Ivies have a long way to go to prove they're offering as much value as the best public colleges. Even at the schools with the most generous aid policies, some students get zilch, and many comfortable-but-not-rich families are staring down the barrel of five-figure student-loan bills. Furthermore, the size of aid grants is often based on the number of children in a family, reducing the generosity for one- or two-kid households.

But for many, the biggest issue may be whether Ivy League degrees still carry the same economic clout in an age when many other schools have worked hard to improve their academic credentials and where liberal-arts degrees no longer necessarily pave the way to high-paying jobs. Indeed, in a study published earlier this year, economists Alan Krueger and Stacy Dale showed that students' SAT scores are a much bigger predictor of future salaries than the school they attend. Kids whose scores were good enough to enter elite colleges eventually earned as much as graduates of those schools -- even if they went to college somewhere, well, cheaper.

What do the Ivies say? Robin Moscato, Princeton's director of undergraduate financial aid, says that if all their grant aid were taken into account, the Ivies would score far better in a Payback analysis. That's a point Harvard President Drew Gilpin Faust is quick to agree with -- adding, in an interview, "I believe the experience at Harvard is unparalleled."

Non-Ivy Private

Avg. payback score: 79
Avg. salary for recent grads: $46,414
Avg. salary for midcareer grads: $94,181

It wasn't an easy decision to make. Paul Ott says his son, Evan, tops in his class and a National Merit Scholar, got into a pair of well-regarded private schools and was offered some impressive grant money to boot. But he found that even the private schools' best offers would leave Evan owing as much as $25,000 a year for tuition, room and board. The Otts, who live in Dallas, will instead send Evan down the road to the University of Texas at Austin, where in-state valedictorians attend tuition-free their first year. "That was huge for us, because we're not well-heeled," says Paul Ott.

Compared with the Ivies, experts say, most of the private- school sector has far fewer resources to tap for scholarships and grants. Indeed, the average Ivy League endowment was worth $10 billion at the end of 2010, while the endowment of the average college was worth only about $400 million. Not coincidentally, the schools in our study cost more to attend, on average, than the Ivies, and their tuition has grown faster since the 1990s. And the loudest howls of complaint may ultimately come from grads whose salaries don't measure up to their college bills. At midcareer, graduates of the schools in this group averaged income of $94,000 a year -- certainly respectable, but 16 percent less than Ivy grads were making and only 6 percent more than that earned by graduates of much cheaper public colleges. As for SmartMoney's Payback Score, this group gets a 79, lowest among our three categories.

Some education experts blame the income lag on these schools' strong identities as liberal arts colleges, noting that those who earn the most in this job market tend to major in other subjects, like engineering or business. At Sarah Lawrence College, in Bronxville, N.Y., graduates often choose careers in education, public administration or social work, and come out earning, on average, just $38,600 after two years. (Officials at Sarah Lawrence say that figure may underestimate alumni salaries but also contend that's beside the point: "Their rewards are measured not just by earnings but by how much they are giving back to society," says Tom Blum, the vice president of administration.)

To be sure, many private schools don't fit the same mold. Indeed, a number of the best-scoring schools in this category -- including Carnegie Mellon University, whose recent grads earn more per year than alums of any other college in our survey -- have strong programs in business and the sciences. And as for that tuition burden, many private schools say they're doing their best to ease it: Sarah Lawrence, for one, is providing an average $31,000 in help per financial-aid recipient this year.

Public Schools

Avg. payback score: 141
Avg. salary for recent grads: $48,486
Avg. salary for midcareer grads: $89,662

If our payback survey were a football game, the public schools would be spiking the ball in the end zone and kissing the mascots. Among recent grads, public alumni earn annual salaries equal to 52 percent of their four years of tuition and fees; private-school kids bring in just 32 percent on average. For out-of-state students, full-fare tuition at the schools in our survey is 35 percent lower than at private colleges, but in many cases, the career options are just as strong. Ralph Mobley, director of career services at Georgia Tech, says 63 percent of May's graduating class had jobs at commencement, up from 53 percent of the class of 2010; computer science and chemical engineering majors were among the hot recruits.

Of course, public colleges have some troubles of their own. As tax revenue shriveled in the recession, many states slashed the budgets of public universities. State spending per college student has fallen by about 19 percent from a decade ago, leaving many schools with bigger classes and beaten-up facilities. To close their budget gaps, politicians have been hiking tuition for out-of-state students. From 1996 to 2009 (the graduation dates of our two survey groups), the cost of a four-year nonresident degree at the schools we studied more than doubled, to $93,500. At the University of Texas at Austin, where out-of-state tuition has grown nearly 70 percent in five years, the average loan debt for undergraduates is now almost $25,000; Tom Melecki, UT's director of student financial services, says this year's budget cuts were "unprecedented in their depth."

Still, the budget cuts haven't yet tarnished the public schools' bargain status. And for students willing to stay in-state, the financial equation looks all the better. Paul Ott, the Dallas father who counseled his son to go to a public college where first-year tuition is free, says they are anticipating getting an additional $2,000 or more in state scholarships from the University of Texas. At a recent freshmen orientation in Austin, Ott says, another dad shared how Texas helped his son land a well-paying job in computer science at a Houston oil services firm after a summer internship. "The fellow said his son is making more money straight out of college than he did after 30 years," Paul Ott recalls. Both the elder and younger Ott say they'd be more than happy with a graduation present like that.

Additional reporting by Sara Germano and Jen Wieczner.