My advice is always to (1) be good at your craft, (2) set constraints, don't just make global maxima decisions.
Regarding (1), take your claim about AI for example. I was at the most recent ICML and EMNLP, and my Fermi estimate's that we had about 250 attendees for every 1 company recruitment booth. To put that ratio in perspective, Google's AI team has a headcount of about 150, and that's probably one of the largest groups. AI is commoditized, and it will be even more so by the time you're at the peak paying stage of your career. Also take into consideration that 5 tech firms have propped up the market for the last 8 years, and that has slowed down rapidly this year. The job market is incredibly efficient, and it doesn't make sense for there to be a systematic salary bias in favor of AI jobs forever, especially considering the barrier to entry is very low.
I run a hedge fund and have come across a wide cross-section of wealthy persons as a side effect of my work. (By construction, we are only allowed to accept investors that are 'QPs', which is about a small group of about 30,000 entities in the U.S.) I've come across people making >10^6/year writing books; doing standup comedy; marketing FX derivatives; selling underwear; doing biology or math research; doing runway modeling; selling maple syrup; being employee n<5 at FB/GOOG/AAPL; taking photographs, and so on. The one thing in common is that they're all amazing at their craft.
(2) is really just a corollary of (1). You can't be amazing at your craft if it's overly broad. Being #1 and biology research or #1 in AI is incredibly difficult. Feng Zhang will probably net a Nobel Prize
and amass a $10^8-10^9 net worth in the next decade, and he didn't get there by being #1 in biology research, or even #1 in genome engineering, or even #1 in utilizing the CRISPR system. A constrained optimization is a lot easier.
@MarneMath's numbers are not as uncommon as it sounds. I'm in the high-frequency space and our numbers are actually slightly higher across the board because of the scalability. I won't speak exactly about our firm, but one of my employees has a physics PhD and netted a $37M bonus in 1 year from generating over $400M for his last firm in a year (his team of 3 was behind 1/10 out of every dollar traded in every single one of the European stock markets), and he was there for 8 years.