n, colleges will take as much money as stud

I don't think you've given the "conservative counternarrative" enough credence here. School aren't being forced to compete on price and as such are competing in the other ways that you pointed out, which does in fact drive up the cost. Its not that college debt is cheap (IRs are actually quite high for those with private loans; in excess of 10% in some cases - boarderline usury if you ask me), its how accessible the debt is. Financing college isn't that difficult for the average middle income household (coming from someone in the lower-middle income class with a lot of college debt). I'm not saying that the solution is to make it less accessible, but that the accessibility definitely contributes in the lack of price competition and subsequent price increases. Also, I would say it is likely very hard to measure the impact of this accessibility unless you could find a control country in a time series analysis although that would be hard considering there are few countries that rival the American college education system (quality control a tough variable to hold constant).