For a long time that marginal cost was Canadian oil sands oil, which cost about $40 a bbl to extract and $10 to ship. The Saudis who can produce at $10 a bbl were making money hand over fist.
That's not what "monopoly" means. Monopoly power isn't just a fancier word for market power. Monopoly power is power derived from the fact that nobody else is selling what you're selling.
Note that in this example, the Saudis can't raise the price of oil above $50 / barrel. Setting a price of $60 would send their sales to 0 rather than to whatever the level of demand is at $60. They can't do it because they don't have monopoly power.
(If you expand the example a little, saying that world oil demand exceeds the amount Canada can produce, then you can claim that Saudi Arabia has monopoly power by virtue of being able to sell oil that Canada can't sell. But in the model where Canada can produce any amount of oil at $50 / barrel and Arabia can produce any amount at $20 / barrel, there is no monopoly power anywhere.)
In what world would any company make zero profits in a "perfect" sense?
Companies exist to make profit...
https://www.investopedia.com/ask/answers/033015/what-differe...
Where does this conclusion come from?
I would intuitively define a free market, as a (virtual) place, where people can trade freely (goods or labour) without restrictions. And they profit, if they are better off with the trade, than without. The more free the market, the less restrictions.
Why so complicated?
Profit is market inefficiency, whether due to missing information or inadequate competition. Perfect efficiency drives prices down to the marginal cost of a good or service. Micro 101 stuff.
No profit = no motive.
"perfect efficiency" means "no market" in this definition. It's a make believe process that will literally never happen. Companies that work with perfect efficiency close their doors.
