There are some people who get a college education strictly for the knowledge. The fact that they receive a degree is secondary. They are trying to attain personal growth. Personal growth is what they value and the college education fulfills the criteria for them.
Other people go to college to get the degree, for them knowledge is a by-product. They may be getting the degree to advance their careers. They could also be getting it to help retain their current job. For these people the degree is what holds value in receiving a college education.
Another person may value the college education for their own self fulfillment. Some people may feel a challenge to be the first in their family to receive a degree. The completion of achieving their goal is what they value.
There are many people that succeed without a college education. These people would probably have succeeded even more if they had a college education. However, I couldn't find any research on this topic. I also believe that there are people that have gone to college that would have succeeded on their own without college. These people are high achievers and very motivated.
Everyone has their own idea of the value of a college education. I wouldn't be in college if I didn't believe there was personal value in it. For myself, the value of a college education lies in the skills you develop, the knowledge you receive, and the networking opportunities you create. I have already seen value in the information and skills I have gathered from my first class. Some of the items could have been learned on my own without the structured guidance of a college curriculum. However, the overall value I place on college would be very high.