Question

Over their whole lifetime, about how much can someone with a professional degree expect to earn compared to someone with a high school diploma who didn't attend college?

Answer 1

Situations, circumstances, and economic quality at the time do factor in, but 2017 reports:
Less than a highschool diploma have an unemployment rate of 8% and earn $25,636 a year.
Professional degrees have an unemployment rate of about 1.5% and on average earn $89,960 per year.