From the article: " Over the course of his working life, a college-educated white male .... will have earned about $2.3 million. His high-school-educated white-male partner will have earned $1.2 million." Let's say college costs $100,000 (tuition plus opportunity cost of income, etc). Now let's say instead of spending that $100,000 on college we invested the money instead at 6% per year returns. That will give you $1…
So let's say that everyone takes this advance and doesn't go to college. How does the economy earn that 6% return?
Those people who don't go to college just go get a job instead. (If jobs need training, they can apprentice or otherwise learn-on-the-job, but they won't be spending half that time learning french literature or what-have-you) Since people are doing something more productive with their time than sit in a classroom, their lifetime productivity improves, hence the productivity of the economy as a whole improves.
Given that college is a bad investment for most people, we'd be better off if fewer people did that. (Though the optimum is probably that some people go to college, not all or none.)