I know it's not all about the money, but over the course of your entire career, do you think that move was financially positive or negative?
I'm very roughly estimating that you could probably have worked in the HFT job for around two-thirds the time you're going to have spent working on generic web tech, and still been better off.
Absolutely 100% positive. I was largely an individual contributor all that time, and only did some unstructured, untrained, unguided people & project management. Perhaps because it was such a niche, engineer-dominated environment. Several years after leaving that company, I quickly learned to effectively manage people and projects, architect systems using more mainstream/open source tech and eventually reached exec level (but that's a different story).
Ah, that's the missing punchline: you had ambitions to be something else other than an engineer, and you (quite correctly) recognised that you were never going to grow your wider skills at such a place.
For someone who had wanted to stay an IC, I don't think the move would have been quite as wise. Being in a niche, engineer-dominated environment, and being paid extremely well for it, is nirvana for many lifelong ICs. It certainly feels very different from the experience of Arthur from the linked article.
That's really some fields I'd love to get into -- less need to talk to people and more need to talk to the machine. What a dream! Alas I only scratched the surface of C++.
I'm very roughly estimating that you could probably have worked in the HFT job for around two-thirds the time you're going to have spent working on generic web tech, and still been better off.