I did a PhD in pure math and now work for a big tech company. Having the PhD will get your foot in the door basically anywhere, so you'll at least make it to the screen, but ultimately you have to pass the same interview as anyone else. That means doing LeetCode and reading Yegge's stuff etc.

If your goal is to maximize lifetime earnings, a PhD is maybe not the right choice, but if you want to spend years studying something you love while financially breaking even then go for it. I definitely don't regret it, even though I would be worth a lot more if I had gone into tech straight out of college.

Btw, finance is also a common destination for pure math PhD's looking to leave academia.