So much figurative blogosphere ink has been spilled over the US News law school rankings that I hesitate to try to add anything. However, there is one flaw in the US News system that hasn't received as much attention as it should. As Brian Leiter explains, approximately 11% (9.75% for instructional spending, 1.5% for other spending) of a school's rankings depends on its per-student expenditure of money. This may not seem like a lot, but, given the high degree of clustering in the other components of the formula, it can actually make a substantial difference to a school's final ranking.
In other words, if School A and School B are exactly equal in the quality of their students, faculty, facilities, etc., but School A spends twice as much money per student to get this result as School B, then A will come out well ahead in the in the US News rankings. A is actually rewarded for being far less efficient in getting educational value for its money than B! Thus, the US News system gives schools an incentive to engage in wasteful expenditures. This is particularly unfortunate in the case of public law schools, where some of the funds expended are taxpayer money. And even private law schools receive many direct and indirect government subsidies as well.
There is no reason to believe that including expenditures provides useful information to applicants or others interested in the school's quality. To the extent that the money the school spends translates into real improvements in quality, these can be measured directly by including ratings for the quality of the faculty, student body, and facilities. Many of these factors are already included in the US News formula and the rest certainly can and should be (some are in fact measured in the Leiter rankings).
I have to admit that George Mason Law School has a lot less money than most of our competitors, so we have a special interest in getting this part of the US News system eliminated. But this, to my mind, is one of those cases where an argument is correct despite the fact that the person making it could have self-interested motives.
UPDATE/CLARIFICATION: It's true that US News does not publish a separate expenditure ranking. However, as Brian Leiter explains in the first link above, they DO factor in expenditures in the formula that determines schools' overall rankings. As a result, some schools place ahead of others solely because they spend more money per student without actually increasing quality.