Opportunity cost of grad school, etc.
Rob Knop liked my previous post. The comments on his post are well worth reading. For example, someone pointed out that, even if you don't go into debt to finance grad school, there's still usually an economic opportunity cost. During the years you spent in grad school and as a postdoc, you might otherwise be paying down a home mortgage, saving for retirement, etc., not to mention nonfinancial opportunities, like starting a family.
Terence Tao also has some good career advice,. It's aimed mainly at mathematicians, but much of it is relevant to science in general.
Of course, not going to grad school could also have opportunity costs, especially nonfinancial ones. If you really want to do research, with reasonable freedom to choose your own research problems, a PhD is almost essential. It's not just a matter of getting paid to do research. A PhD-level position is also needed to get access to all the expensive equipment, and grants to pay for expensive supplies, needed in most of science today.
Because it's a much smaller commitment, I often encourage students to consider doing an MS (2 years) before deciding whether to tackle a PhD (4-8 years plus 2+ years postdoc). An MS is good background for various science-related jobs, including teaching high school science, most technician jobs, etc. Nobody ever takes my advice, though, maybe because it's usually not that hard to switch from a PhD program to an MS.
A technician, often with an MS or even BS, doesn't get to set the direction of a research program, but, in the right lab, is a full-fledged team member with plenty of opportunity for scientific creativity. There's a little less job security, relative to a tenured faculty position, but my prized technician was snapped up by another lab when I left UC Davis.