Earlier quoted context omitted.
> In the sense of benefit to the overall economy, to the society in which that economy sits, or to humanity in general, virtually all economies of scale are actually harmful You had me until here. Economies of scale in commodities is the thing that makes it so we don’t have to do sustenance farming and everyone gets to have sewn clothes on :) There’s truth in both sides there - we want nail production to not be done…
I guess I forgot to repeat the part about "extremely large" there. But I mean like "all economies of scale beyond a certain point". In any case, I'm not sure I agree that economies of scale are the thing keeping food on the table. Like, yes, we want nails to be made in some efficient way, but that's not what I mean by "economies of scale". What I'm talking about is the size of the companies involved. If there are 10…
Well, a nail is fungible, as are many other products. So what you'll end up with instead is a bad situation on its own.
The 10 nail factories win sales contracts by competing on price (obviously), so there is a massive incentive for the companies to undercut each other by going offshore, exploiting their staff (which usually leads to an enshittification across the industry), exploiting the environment (by "saving" on emission mitigation or outright handing waste over to the mafia instead of recycling) or by cutting corners in the process (water down the material composition with cheaper raw materials or be less strict in outgoing QA and hope the customer doesn't notice). In the end you have 10 companies shipping crap nails but since they were so much cheaper than what was there before, there are no high quality nails on the market, and no bank will give anyone a loan to try and start up a company selling high quality nails.
We've seen that happening quite often over the last decades... UK and German public transport where the "private" competitors have reduced staff and maintenance to the utter bare minimum, "chinesium" being so widespread it's a legitimate meme, or by Europe being completely dependent on India and China for basic pharmaceutical compounds.
In contrast, a government controlled (or outright owned!) monopolist has entirely different priorities, and the customers/citizens will get high quality products again.