There's a couple of things going on there. No question that the cost of college has gone up. But so has the price of everything. So while college outpaced inflation for a while, BamaNation's numbers show that it's levelled off versus inflation.
Also, chanson78's excellent research shows that, while the cost of college may have risen, the inflation-adjusted amount of student debt per borrower hasn't changed much over a long period of time. Which would indicate that, as a whole, today's students are doing what we did -- working, getting scholarships, and cutting living expenses where they can. Having worked on the National Alumni Association's Scholarship Committee, I can tell you that there's a ton more scholarship money available today than there was when I was coming through, even adjusting for inflation.
It just strikes me as illogical to say, "Never mind the fact that your debt load isn't appreciably greater than previous borrowers', we're going to forgive what you owe because the cost of college has gone up."
You also make a good point about tuition not being the only cost of college. There's obviously room and board. But whether you're in college or not, you have to live somewhere and eat something. So unless you're living in your parents' basement (which has its own set of non-monetary costs), and they're not charging you for your food, the net marginal cost of college room an board is not much, if anything.
Tuition is a true marginal cost, as are books (including a computer there) and all the various fees that colleges charge for this, that, and the other thing over there. If I were benevolent dictator, I'd call the cost of college tuition, all fees, books, and a computer.