Earlier quoted context omitted.
Note some good US universities pay entry-level FAANG salaries to assistant professors. If you can negotiate a low teaching load, it might be OK in some cases. Nonetheless, I agree with what you say. I'd add there is a ton of nasty politics, bullying, etc. which might be hard to avoid while you are on tenure track chasing tenure.
The opportunity cost is still likely 100k/yr for the rest of your life, even with the FAANG salary to assistant professors. consider this: You can be a new grad, get hired at Apple, and earn an entry-level salary[0]. Let's say we won't include the bonus and you get 130k/yr. You colleague is a new grad and goes to a PhD program at Duke University[1] where they earn 33k/yr. In your first year, your PhD program colleagu…
First, faculty salaries as reported are typically 9-month. There's an extra 3 months of earning potential for professors, where they are effectively free agents. They can spend that doing research, or any number of other activities. Or nothing
Second, professors own their work product. If you are a salaried employee at a corporation, everything you do on company time is owned by the corporation. If you try to sell your work product or take it to another job, you will likely be fired and/or sued. This is not true for faculty; we own our lectures and all the content we produce for our courses. We can take it and use it other jobs, sell it as a book, make it available for free, or anything.
Third, we own our own time off the job. I'm free to run a consultancy even though I'm employed full time as an academic. I can make as much as I want through that, and people are willing to pay what I want because of my degree and my affiliation with the institution I work at. I doubt Google will let you trade on being a Google engineer while working at Google. Indeed, most FAANGs have a clause in their contracts stating that they basically own all ideas you think of, whether on or off the clock. If you're willing to take their salary for that kind of trade, then you might think it's worth it. For academics, they think perhaps they will have a good idea one day and turn it into a startup or patent it, and many do.
Fourth, I have control over a lot of other people's money. So while I'm not paid a lot, I get to use millions of dollars in funding and equipment. If I move to another university, I can take my money and my project with me. I have hundreds of thousands of dollars of sensors and equipment in my office that I've bought over the years that I personally didn't have to spend a dime on, but which is pretty much entirely mine to use.
All this is to say that a straight comparison of salaries isn't going to get you the full story. For instance, is there any amount of money you can pay such that you can take 3 months off every summer, and still have a position in the fall? How much would you pay your company to own an idea you had on company time? Do you have an office with a door? Do you have an assistant? Do you own what you work on?