They don’t tell you this in Bio 101:
Ars Technica, The Tenure Track Not Taken:
Becoming a university professor requires a lot of work for very little financial reward, compared to most other professions. In STEM (science, technology, engineering, math) fields, the minimum requirement is four years of undergraduate education, plus anywhere between four and a half and eight years of graduate studies, followed by an (ever increasing) number of years of post-doctoral work. That may get you an assistant professorship where, at a state university, the starting salary is in the $60k-70k range.
(The only other career path I have seen that has similarly low pay for exorbitant requirements is becoming a chef. In both cases, you only do them because you simply love doing them.)
To be fair, starting salaries in the life sciences at major research universities are better than 60-70K, and are in fact competitive with starting industry salaries. Why do I do this? ‘Because I love it’ is a little too trite. This can be a desirable career because 1) the autonomy available in an academic research career is hard to beat unless you’re independently wealthy, and more importantly, 2) there actually aren’t that many places outside academia where you do science the way you imagined it would be as a naive undergraduate, that is, defining your own interesting questions and going about solving them. In most (but not all!) industry settings, you will spend most of your time working on a research question defined by someone else.
The Finch and Pea 
Much to be said for teaching bright high school kids. There’s little prestige, but the financial rewards are better and students, at the AP level, are bright, open, and ready for any real challenge. One caution for the mid-career switch–all your social security will most likely be lost. To get the best retirement, teachers would need to start by 35. BTW–it is harder work.
After my time as a grad student and post-doc, I don’t have any accumulated social security benefits anyway…
Teaching is certainly a rewarding and important career choice. I think the key to successfully negotiating a science career is to know in advance what the expected starting salaries and training requirements are for various options, and calibrate the length of grad-school/postdoc experience accordingly.
If you’re looking at an option that starts at 60k, beware of the opportunity costs of a long postdoc.
Fortunately, by keeping postdocs and grad students artificially poor (i.e., paying them much less than the recommended salaries from the major granting bodies) they really make 60-70K look great. That can be a 20-30K raise for a postdoc, which looks really good relatively speaking.