> Student loans are some of the least-risky loans to give

You can't shed student loans through bankruptcy, which is another big problem in the same vein driving up costs.

> there is a thriving private market for non-government guaranteed student loans

To my understanding this is not the case. The market is dominated by government backed loans. Correct me if I'm wrong. I'm pretty sure "peripheral" is a better choice of word than "thriving".

> Today universities are centers for research and have much broader educational missions.

This really doesn't address the issue. It should cost the same in real dollars to graduate an English major as it did 60 years ago. Realistically, it should cost less due to economies of scale and technology. Instead it's many times as expensive.