Hi
@BlackCatsAreNice and thank you for sharing your reflections with the community. You mention a sale or two, but not sure the portfolio size, so not sure what that means. If you have 25 domains and sold one for $$$$ that is probably doing better than industry average. If you have 1000 domains and sold one for low $$$ then not.
I think too many people under-estimate how hard domain investing is. Not only do you need to learn and study lots of things, be analytical and logical, work hard, and more, even with all of that, it is no sure thing and often will be a long time between sales. Domain investing is not assured, easy or fast.
As has been mentioned by others, probably most people in domain investing lose money. I suspect the industry average is near break even or slight loss, but because a small minority make good money that means that most will lose money. With wholesale prices going up in recent years, and with registries in new extensions keeping the best for themselves, and with caps off most extensions and increases in renewal rates for .com approved, it makes things even more challenging.
Even models such as the one Paul Nicks presented at NamesCon 2019 showed that the break even point was after four years, and not significant monetary return until year 6 (this was for a domain investor buying in the expired auctions and selling at as I recall low/mid $$$$). There was eventually a good return, but many tens of thousands had been spent, and no return on time, in the years leading up to that.
It is interesting that you mention domain development, as in compiling responses for the 2020 projections it seems to me that more people than in past are looking at that.
The very best wishes for your future pursuits. It speaks well of the NamePros community that several have reached out to offer you assistance if desired.
Bob