The OP's chart is meaningless because of selection bias. Presumably, the college grads would be more employable because of higher intelligence, greater access to resources or better habits, which led them to college (I know there are many exceptions to this).

The real question is, what would many of those college grads have done otherwise in those 4 years, with the money they would have saved?

FWIW I learned a ton about myself in college and wouldn't trade that experience for anything.