I think that depends a lot on the location. I know a couple of people who do PhDs in Japan and they are a lot less well paid than German PhD students. I expect that this difference persists even after they graduate.
Very true. These are rates in the SF Bay Area and NYC. IDK what it's like elsewhere, though I've been told it's possible to get offers in this range in London too.
East Europe universities, particularly lithuanian (VU and KTU) pays about 300$ per month for PhD student.