The point is that one needs to gather all the information available before making a judgement about what to study, including what their priorities as a person are. If teaching makes you happy, then teach. But don't whine when you make 70% of what your peers make (a. you're still making a living wage, and d. you get a shitload of time off). Finding a career that speaks to you is going to be the best decision that you can make for yourself. Someone is always going to have more money that you. Who gives a shit?

I would always suggest studying that which you are passionate about rather than that which will make you the most money. If, years down the road you find that you would rather earn more money than continue in your chosen career, there are a number of ways to make a lot of money that don't require a formal education. The decision would become more difficult when there are two things you are passionate about and one of them you are just slightly more excited about but it pays 1/3 of the other. This is when I might actually suggest picking that which you are still excited about but perhaps not as much as the other, in order to make more $.

Also, money isn't the only ROI that should be measured in this situation. How many more hours did you work as an engineer? How much less flexible was your day? Quality of life isn't measured in dollars alone. In fact, I'd suggest the dollars are at the bottom of the list for most people. 1. Autonomy -Can I control when and how I work. 2. Mastery -Will I have the ability to get better at what I do and grow my knowledge and ability 3. Purpose -Is what I'm doing having an impact? Then.... money. If you've not watched the Daniel Pink RSA Animate, check it out.