For me earning a PhD was not about the money or wealth creation. It was about the chance to work on a exciting research project that could make a real difference and contribution to scientific knowledge.
Besides, in the UK at least the scholarship funding is not bad at all. I found the £12K per year tax free funding was easily enough to be comfortable on whilst doing my research.
I think you could say that they are funded well, in the sense that no one should be paying out of pocket, but that is different than saying that they get paid well. It depends a lot on school, location, and (possibly) subject.
I think the typical engineering PhD major makes close to the equivalent of 12,000 Pounds. It's usually around 16-18 starting from what I know. When you're doing something that benefits mostly yourself (getting a degree), making that kind of money is getting paid well, in my opinion.
Besides, in the UK at least the scholarship funding is not bad at all. I found the £12K per year tax free funding was easily enough to be comfortable on whilst doing my research.