Is a PhD worth it?
Personally, it was worth it for me. I was fortunate to work with amazing people like Bill Dorland, Alex Schekochihin and many more. And I got to work on fun problems.
But, if you are asking this question, it probably isn't worth it for you. You should only do a PhD if you are so hell bent on doing one that no one could convince you otherwise. There were many who tried to tell me it was a bad idea to do a PhD, but I was not to be convinced.
Don't get me wrong, a PhD can absolutely be worth it. You get to work on something that you (hopefully) love. You get to push the boundaries of human knowledge. It is literally one of the most impactful things to do.
It also grows you as a person - you become better at learning new things, at systematically breaking down a problem and chipping at it till it becomes manageable. You learn to communicate your work to a wider audience. You develop a confidence in yourself that you can take on gnarly, seemingly impossible problems and just figure it out.
However, a PhD is a long and painful journey. It can be quite lonely. So if you have even the smallest of doubts about whether you should do one or not, then don't. Especially if you think it might be a stepping stone in a career outside academia. More than likely it is one, but that is not motivation enough to actually stick with it during.
Having said that I really enjoyed mine, so if you are that focused on it then go for it! It's also not a one way street. People do go back to doing a PhD after a career in industry - my good friend satej is a great example! After a successful career at Palantir he decided to spend some time in academia, and seems to be enjoying it.
If you are someone who is trying to decide between a PhD and a career in the industry, hope this short writeup helped. If you have any questions or want to discuss further, do get in touch - I am happy to chat.