"Is there another economic explanation that could account for the difference between then and now?"
Of course. As government subsidies for higher education (Pell grants, subsidized and readily available student loans) increase, so too do tuitions. They'd be stupid not to suck up all that easy money. It's not simple supply and demand, as it's not anywhere close to a free market.
Just wait (probably until after the next administration) until "free" college becomes the norm, people with student loans are expected even less to keep their commitment to pay them off, and we go even further down the path toward a lack of any personal responsibility. For a reality check, see what the government says in headlines
- "Grants and scholarships are free money." Obviously written by someone with a liberal arts degree and no understanding of economics, or the true costs associated with "free." If higher ed is "free", expect even more degreed programs in underwater basket weaving.
I truly feel sorry for millennials - things are going to be hard. People voted themselves a dole long ago (accelerating around the 2nd Roosevelt), and it was the following generation which got the benefit - with the bill left to generations beyond them. And that's continuing. It sucks to be you, but thanks for funding the bankrupt Social Security system for me, which was robbed to pay for other welfare programs, leaving a big paper IOU.
The sad state of affairs is that millenials deserve it. Instead of waking up to reality and becoming fiscally responsible, what I see is younger generations expecting even more government subsidies, creating an even larger problem to kick down the road. You and your children will reap what you sow.