There is no easy answer to this question. Unlike other in this thread, I am answering the OP's question at face value (i.e. what is the most _lucrative_ profession) and not considering happiness, etc.
I agree with OncoCap about Insurance Actuaries. I would also add business owner to the mix (even small business owner.) In terms of return of $$ vs. "investment" in education, I think Real Estate is up there, since you don't even need a college degree to sell Real Estate. If I were just looking to make a lot of money fast, I would look to one of these professions. Also, I agree with another poster that said entertainer, but I think the OP mentioned something that was statistically probable, and I don't think that entertainer fits that bill (even the [highly-paid] adult entertainment business is very competitive nowadays.)
However, any professional job can be lucrative. Doctor, Lawyer, Engineer (As someone who lucked into the high-tech boom of the late 90s, I can tell you first-hand that, under the right circumstances, engineering can be VERY, VERY lucrative 🙂 ) CPA, Investment Banker (SDN's Favorite,) Professor, etc,e tc can all be lucrative. The general rule is that you get out of something what you put into it. Identify your character strengths and weaknesses and pick a profession where you fit (i.e. if you don't like selling things, Real Estate may not be for you.) If you bust your a$$ and are good at what you do, you will probably be financially rewarded in any Professional Job. There is no "magic" no-brainer easy-money job (becuase if there were, everybody would be competing for it.)