You are laying a tough question on the table. But you are not the first. Look here.
The difficult part of your question is who is who, or better who is what. That’s why I leave out names.
There is a limited quantity of manufacturers of $500+ lights that you can buy via their website. Number of people working there is limited. As is number of models. Output is modest. Quality is extreme.
On the other hand there are large companies with large factories. Output is enormous. Quality is high. They are not into the lumens-battle, but into market-share. Some rely heavily on large contracts and employ more lawyers than engineers.
And then there is quite a variety of brands who do their own design but outsource the physical aspects. The shops who make the parts are payed for their material and hours. Leaving the largest risk with the owner of the brand. Or small companies who buy unbranded parts from third parties and put their name on the assembly. I could be wrong, but IMHO this is how most of the brands we know operate.
This can result in a (limited) potential of lego-ability of parts, like bodies and tail-sections, between brands.
On the other hand there are big sellers who start their own house-brand and sometime even succeed in making parts that don’t fit where they should.
And last but no least there are people who purchase batches of lights from main-stream manufacturers and try to make a living selling the modified lights. Or people who design and make improved parts for certain lights. An end up selling complete lights that are in every aspect better than the original.