Thank you for this post.

It seems to me that your observation in the first paragraph - "As these firms compound in power without much apparent profit, one can’t help but see them in their own category" - is written through the lens of the corporate ecosystem. Broadening the perspective reveals a decently-sized population of well studied, deeply analysed entities that inhabit what might be the same niche: nation states.

Nation states can be seen as organisations that exist to further the interests of the ruling elite and/or population rather than to fill state coffers per se. Among the many facets of this role are: controlling trade flows and routing them in some way through the nation state; amassing and projecting power; providing a stable, ordered environment in which to conduct business - including maintaining the rule of law; and making available to the population everything needed to live the idealised life promoted by its particular culture.

Amazon et al make more sense in this context and I would be interested in economic and financial analysis that made use of macroeconomic approaches and tools to investigate them.