Overworking, but probably not underpaying. I remember hearing about how much a SpaceX intern was payed and being shocked (it was several X my scientist pay)... Then she told me how many hours she was working, and it made some more sense (but it still seemed high -- scientists often also work 80+ hours)
I work in the same industry as SpaceX. They are in fact well known for pay that would be average-at-best in a sane work environment coupled with an absolutely insane work environment. When I was in college, my only goal was to get a job at SpaceX. After getting a few internships and talking to some people in the industry, my only goal now is to never be so desperate for work that I accept a job at SpaceX.
Their intern pay was also in line with this. I got paid a little bit less as an intern at NASA, but much more as an intern at a non-aerospace (also non-FAANG) tech company.
Getting paid what seems like a lot is not the same as getting paid what the work you're doing is worth.
i.e., did it seem like a lot "for an intern"? Did it seem like a lot when you take into account what was expected of them? I mean, if interns get hired to jobs that seniors (for the sake of argument) should be doing, and the interns are getting sub-senior pay, then they are underpaid.
When I worked at SpaceX I had one of the saddest comp packages I've ever had in a long career. I left for a competitor and got 35% more just walking in the door, plus I don't have to deal with an inhumane company culture. I honestly don't know what Elon is going to do when he runs out of people to chew up and spit out.