For most jobs in business, starting salary is similar, but then everyone diverges. There so many different kinds of positions with different responsibilities. So it's hard to predict what you're making say after 5 or 10 years of experience. I'm not sure about MFE or Quant since I haven't started yet, but studying in a Business School, I can tell you 40ish week options are very rare out of MBA. I think consulting might be least workload (and it does pay good, so you might want to investigate), but you travel a lot and workload is inconsistent. Even then, I'm not sure if they average 40 hours weeks. Generally, you have to remember most important positions are working to earn profits or accomplish projects. Sure you can stop after 8 hours every day, but things still need to be done by deadlines. Although, I think Actuaries work 40 hour weeks. I'm not sure how much they make though.
I do think if you want stability and consistent high earning power, Medical school is the way to go. The profession has a very high floor and the average doctor definitely makes more than the average person in finance. Maybe, like some people say even over 90% of the people in business. Furthermore, its very stable and isn't affected by business cycles. Of course the catch is that it is expensive to get through Med school.
Well, running a business can potentially be rewarding, but it entails high risk. Most people starting businesses make very little. Ony a few succeed. A salaried job is at least fairly secure.
That being said, I do agree, you will never make a lot of money working for someone else. You have to have some equity or profit sharing partnership and be working for yourself. Most salaried jobs have caps under a million a year.
I personally think the most efficient way to earn money is to work a regular job and invest your savings into etfs. Then you can put all your efforts into your primary occupation and make a consistent salary, while earning some interest that takes little time and effort.