My comment was purely rhetorical, and that was partly my point. The other part of my point is that no matter how carefully you try to account for the costs and benefits of some activity, there are intangibles and benefits that are extremely difficult to convert into dollars (much like the value of a human life when expressed in dollars).

(My comment was not an attempt to refute or disprove the main thesis, but I do think it's important to step back and ask: "what's the point of education? is the point just to make a profit?")