Overall, I agree with your larger points, @MWolf. A PhD is all about research, and is a long term commitment. But…
80-100 hours/wk for 5-7 years? Not in my experience…
During the 1st 2 years (when there is a lot of coursework), 40-50 hours of actual disciplined work, and 50-60+ hours in the run up to prelims is common enough. Once you move over to all research,(with the exception of brief pushes to get something out the door for a deadline), a well disciplined full-time work week is more typical…
…but! since people who are doing a PhD typically love their subject, the time spent can grow, because just as you are about to finish for the day you find an interesting study that might be relevant, so you just take a few minutes to look at it more carefully and…time slips away. Or, you are working on an analysis and something unexpected pops up and you want to see if this is an actual find or an anomaly so you try changing the variables and…time slips away.
In other words: if you really are interested in the research you are doing, the actual doing of a PhD can be (whisper it) more fun than not The luxury of being able to take a deep dive into a question and see where it leads? to poke and experiment and theorize and test? Yes, it’s long, and some of it is a slog, and there is definitely a mid-point slump that takes will to get through and the viva is always going to be anxious- but a lot of it is genuinely interesting, engaging, even invigorating. Add a supportive supervisor and your cohort of fellow students, and you have a community with whom to share the process, both intellectually and practically.
Re prestige- undergrad institution matters more in some fields than others (philosophy v physics, for example). But, even where it matters a lot, other things matter as well- the quality of the research the applicant has done, the calibre of the writers of the LoRs and their evaluation of the potential of the candidate. And, for a PhD the ‘fit’ of the research interests and research background is particularly relevant.
Re: demographics- it is true that Econ has a terrible track record in terms of diversity. Only about 5% of UG & Masters degrees in Econ go to Blacks/African Americans in the US, and about 3% of PhD’s. But the OP is coming from Chemistry, so this is not unfamiliar territory (6% and 4% respectively). And she gets the double whammy of being female, who are out-demo’d 2:1 in Econ. As the mother of a grad student who will be out-demo’d in her field for her entire career (the ratio is currently 88:12), I have seen some of the ways that plays out. It is also why I emphasized getting to know the departments well- my gradschoolkid ruled out several top names in her field b/c of the experience of the current (female) grad students. It’s not just % that matters, it’s attitude.