The US makes for a good argument against pay-per-use education. Crippling student debt and huge numbers of students who don't find jobs that pay a living wage.
Then you have "predatory" private for-profit universities like the University of Phoenix...
They didn't make this stuff up: http://en.wikipedia.org/wiki/University_of_Phoenix#Governmental_lawsuits_and_investigations
The PERI institute at University of Massachusetts Amherst calculated that providing free higher ed for everyone who wants it, and even accounting for the higher demand if it's free, would cost the taxpayer the same or perhaps less than administering the current student loans system, which is heavily subsidised by the taxpayer anyway; students, taxpayers, the economy in general, and society alike lose out from the current student loans system. The only people who get rich are the banks... as usual.
In the UK the Tory govt. proposed student loans to the banks. There was such a push back from the public that the banks decided not to get involved, so the govt. had to set up (AKA subsidise and guarantee) brand new companies to administer them. So the UK ended up with a govt. pseudo-private bank sucking taxpayers money out of the economy for no justifiable reason. AFAIK, it hasn't changed.