There is another factor in your analysis. Education may have more than purely local advantages. That is, it may be a good investment for me to fund other people

There is another factor in your analysis. Education may have more than purely local advantages. That is, it may be a good investment for me to fund other people to get a college education, even if they regard it as a hobby. For examples: I may run a business producing collegiate sweaters, so want more people in college, I may enjoy telling bad puns about philosophers and am willing to pay for others to learn some philosophy so I don't have to explain myself all the time, and we as a cultural may be on a better footing if there are more people who understand the historical development of the US - even if that history education has little direct economic benefit to the person who received the education.