Missed the post at the time, but Matt Yglesias summed things up quite nicely on Wednesday:
The underlying issue… is that there’s very little in the way of reliable information about the quality of undergraduate education in the United States. Our major schools get to select which students they admit, which means that when you’re looking at data about the achievement of graduates it’s hard to know if you’re looking at quality education or just quality inputs. We know that it’s much harder to get into The University of Texas at Austin than the University of Texas at El Paso, so the mere fact that graduates of the flagship campus do better doesn’t tell us much of anything about the quality of instruction. Consequently, “signals” and prestige wind up being hugely important. This, in turn, is an important driver of ever-higher-tuition.