People will tell you that college graduates live longer, earn more, and have happier lives than those who don't go to college, and they have the statistics to back them up. So college can be valuable, at least by one yardstick. The economic value of college is probably a good bet, but it is not a sure thing. After all, a college graduate is an individual, not an average. Well, let's consider individuals.
Human beings are more than economic units which produce goods and services.
The grandmother who returns to college after a working life is probably not seeking to increase her earning power. The value of college to her is likely to be something other than preparation for a good job. She may be seeking personal growth. She may want to develop new uses for her abilities. She may come to campus for the joy of learning.