It depends on field and more importantly, country. I was the last person in my year (that I know of) at CMU to get a PhD, a whopping 9 years after we started. A friend had to re-enroll to get his 10.5 or 11 years in.
Meanwhile, I knew tons of people who got PhD's in CS in 4-5 years back in Australia. They typically did zero coursework or breadth stuff, and they were able to start dissertation work within a few months of the clock starting on their degree, without the undignified business of having to propose their thesis formally in public or even defend it in public.
The process of getting a PhD isn't order-of-magnitude different from field-to-field or place-to-place, but there's definitely a good factor of 2-3x between the most arduous process and the least (which does not mean that one degree is 2-3x better, of course).
p.s. Extraordinarily gifted and organized students at CMU were referred to be "on the 4 year plan". Interestingly, some of the most speedy completers of their PhD work were among the least well prepared for the MSc coursework - there was very little correlation between people who blitzed tons of coursework fast with high grade (the 'hares', like me) and the 'tortoises' - who seemed to struggle with the breadth requirements but had solid research ideas that they plugged away on from Day 1. So a woman who didn't have a formal CS background and completed her MSc requirements slowly was the first person to get a PhD in our year.
Meanwhile, I knew tons of people who got PhD's in CS in 4-5 years back in Australia. They typically did zero coursework or breadth stuff, and they were able to start dissertation work within a few months of the clock starting on their degree, without the undignified business of having to propose their thesis formally in public or even defend it in public.
The process of getting a PhD isn't order-of-magnitude different from field-to-field or place-to-place, but there's definitely a good factor of 2-3x between the most arduous process and the least (which does not mean that one degree is 2-3x better, of course).