My wife has been doing taxes for a few people at Facebook (including engineers and PMs) -- many of them make an absurd amount of money. (>$800k / year)
As long as she doesn’t associate names with those salaries in the conversation, i don’t think it’s unethical. Or she doesn’t act on those salaries and commit some kind of security fraud, it’s just a conversation.
It's no different than with an ER doctor. They can say "some idiot wearing a McDonalds uniform came in with a bottle stuck in his ass" but they cannot say "John Smith came in with a bottle stuck up his ass."
That's great for the ones that make that much, but this kind of information is what's causing Bay Area housing and rent prices to sky-rocket. I have worked with multiple engineers in two large corps and most people make anywhere between 100k and 200k.