It would be interesting to see some study on the big picture here.  What has happened to all the factors?--tuitions, scholarships, available loans, maybe the student job market (not sure that could be measured--but maybe how much of student expenses are paid by student earnings today versus the '70's.)

My impressions on this are based on reading about some of these factors individually (like I think you are right that tuitions have gone up rapidly), and on anecdotal things--family and friends' children's experiences.

Have scholarships increased for example?--I think endowments for private universities have, but I don't know about scholarships.  

I'll look around, but I haven't seen such an all encompassing article.