Worth noting that most of this is a very US view of PhDs. In Europe most PhD students earn pretty close to what their starting salary fresh out of school would be.
Also in Europe the concept that PhD means you want an academic career doesn't seem to be as true. I work with a lot of people who have PhDs and none of them did it because they wanted an academic career. In fact going back to get your PhD after working for a few years is surprisingly common, and in many cases your employer will partially sponsor that.
It is well-known that UK doctoral scholarships (as well as postdocs) are pretty low, especially considering the cost of life there.
In the rest of Europe, grandparent's remark mostly holds. In France, for instance, students get bout 1.7kEUR/month [0], and life is cheaper (unless you're in Paris). Maybe you'd get a slightly higher salary in a company, but the difference is not that big.
For germany, I've heard of people getting around 2.7k € per month in CS (so around 32k € per year). Definitely below industry starting salaries (which are around 50-60k as far as I heard), but still decent.
Also in Europe the concept that PhD means you want an academic career doesn't seem to be as true. I work with a lot of people who have PhDs and none of them did it because they wanted an academic career. In fact going back to get your PhD after working for a few years is surprisingly common, and in many cases your employer will partially sponsor that.