Vassar is also a top university.

It's really hard to justify spending that kind of money for an undergraduate education when good state schools are accessible and are much cheaper.

Sarah Lawrence, Vassar, Kenyon and Bennington are top-tier liberal arts colleges; Wesleyan is a major research university.

The reason you don't see Ivies (with the exception of Columbia) topping the tuition-cost lists is because of their tremendous institutional endowments (just try doing a search for "ivy" and "endowment"--you should come up with a handful of news articles about the latest funding pushes, all in the neighborhood of $4 billion). To get an Ivy-caliber education without an Ivy-caliber endowment requires a heftier tuition bill. The education a student gets at the "little Ivies" is substantively different than the one that she'll get at a state school (I won't say categorically better, but definitely different), and people are willing to pay for that difference.

P.S. This is just a guess, but I'd be willing to venture that Columbia's tuition bill is higher than the other Ivies not based so much on endowment as on the "room and board" line item. New York is far more expensive than Cambridge or New Haven, despite the fact that Columbia is among the city's top five real estate holders.