Just as a datapoint, how I got my doctorate:
Start with a B.Sci (in my case, with a double major in Psychology and the History and Philosophy of Science). First year Psych has about 1,000 students enrolled; by the time you get to third year, that’s down to about 300.
Of those, around 60 are invited to spend another year doing an Honours thesis, which consists entirely of original research. When students ask how much time they need to commit to this research, the standard answer is “all of it”. I lost around 1/3rd of my body weight during Honours, purely from stress.
Of those who complete Honours, about 20 get a first. Without a first, you have virtually no chance of being accepted into a PhD program.
The PhD program is not “education” in the way in which it’s usually conceived. You don’t go to any classes, you don’t read any textbooks, you don’t sit any exams. You just work in the lab, sixty to a hundred hours per week, for about five years. At one stage I spent six months working midday to midnight, seven days per week, without a day off.
In my field, Professors spend all their time attending conferences, giving lectures, schmoozing politicians and writing grant applications. Almost all of the hands-on science is done by grad students and postdocs.
By the end of my doctorate, I’d published about half a dozen research papers, written a bunch of magazine articles, given a score of TV and radio interviews and answered countless emails from random members of the public asking about my research.
All of that was done with no income apart from a couple of scholarships and a bit of casual teaching pay. Money is tight, social life is nonexistent, mental and physical health is sacrificial.
Here’s the thesis, if anyone is curious: http://www.academia.edu/4685805/Mephedrone_in_the_Rat_Mechanisms_of_Action_and_Adverse_Consequences
(squick warning: gruesome image on page 1-8)
The table of contents is seven pages long. There’s a table of contents for the table of contents. 
