> I think it's a valid assumption if the market were comprised of a lot of highly competitive firms rather than 3 not-very-competitive-at-all firms.
Consumer goods are generally highly competitive. There are no monopolies or exorbitant profit margins. The number of companies is irrelevant. Even if it was just a single company, as long as the profit margins are low, consumers are not at risk of being overcharged.
Outliers are companies like Apple, which have a monopoly on their IP, but that's a different story.
For GM, it's probably about 4-5% average in the last years:
https://www.macrotrends.net/stocks/charts/GM/general-motors/...
> I think it's a valid assumption if the market were comprised of a lot of highly competitive firms rather than 3 not-very-competitive-at-all firms.
Consumer goods are generally highly competitive. There are no monopolies or exorbitant profit margins. The number of companies is irrelevant. Even if it was just a single company, as long as the profit margins are low, consumers are not at risk of being overcharged.
Outliers are companies like Apple, which have a monopoly on their IP, but that's a different story.