I believe the cost-benefit analysis you speak of desperately needs to become part of public consciousness sooner rather than later. We can't rely on students to have the maturity and direction to maximize their college experience, but we also cannot rely on them to succeed without
any educational structure for precisely the same reasons. There should be something in place, but it is often predatory under the current paradigm.
In my opinion, college as a publicly subsidized institution of educational breadth needs to end. I think that we could move towards reducing the current burden by doing the following:
1. Privatize student loans entirely, and give them eligibility for bankruptcy.
2. Eliminate all degrees that do not demonstrate a true specialized skill in the manner of a vocation, or a level of academic rigor that cannot be achieved outside an academic setting.
3. End the cultural stigma against those without a college degree.
4. Regulate the use of college as a requirement in job listings, and disallow it as a filter unless it can be specifically demonstrated to be required for a specialized skill (through legislation, if necessary).
5. Reduce the number of courses in an undergraduate degree. Get rid of courses that are not "in the major", and supplement what's left with practical subjects that are critical for personal success (taxes, personal finance, etc).
I don't think this is ever going to happen. But I do earnestly believe it would be the best possible outcome. It's also imperfect and a message board comment obviously cannot flesh out the implementation details. But it's a start!
Privatizing student loans and allowing the debt to be relinquished through bankruptcy would provide a free market incentive for eliminating degrees that are generally unproductive. There are many courses of study aside from the stereotypical "basket weaving" which are taken because kids simply don't have the maturity or direction to understand what they want to do or accomplish with a degree. These harm more than they help, in my opinion, because they forget most of what they learn anyway.
Ending the stigma against the choice to go without a degree could help drive people who would otherwise get poor degrees to go into practically useful vocations, at least until they decide they'd like to do something else. It might also lessen the stigma of adults who return to college later than "college age."
Regulating the use of college as a professional filter would be tricky, because historically this seems to bounce it some other form of signaling (it used to be an IQ test, then it was college, etc). But it might tighten the loop between a choice in major and a choice in career, which is acceptable if it becomes culturally okay to make that decision closer to when the brain is fully developed and if the time required for the degree is shortened (e.g. you could simply go back, if you want).
Finally, you'd help accomplish that last point by reducing the number of courses required for a full degree, potentially bringing the time to complete an undergraduate down to two years.
In my opinion, the ideal of undergraduate education is somewhere between the current Master's degree and vocational training.