I'd put it this way.

An economist would say profits go to zero if markets are really free. Like if there were no barriers to entry and consumers chose purely on price firms would keep entering and would always be incentivized to lower prices to get the sale.

There are barriers that are natural, like "I already have a relationship with vendor A", or "I really enjoy brand B", "I'll have to invest a lot of money to start this business and I won't do it if it seems unlikely I'll make a profit", etc. Then there are barriers like "we have a patent on this technology", "we own a copyright on this movie", "we control the distribution channels", "we pass laws to get keep out competitors."

Business is all about finding ways to beat the economic constraints and ensure you get a profit!

The best case you can make for our system, in my mind, is that there is competition so that vendors have an incentive to provide good products and services at fair prices. Sure, there has to be enough profit to attract investment, but our system works better for all of us when regulation encourages competition.

There are businesses that are highly profitable even in a commodity market. Profits go to zero on the marginal supplier in a perfect market. Any supplier who has a lower cost base than the marginal supplier is profitable.

The canonical example is oil. It costs about $3 to pull a barrel of oil from the ground and pipe it to port in the best oil fields of Saudi Arabia. OTOH, Canadian tar sands cost $50 to pull out of the ground and another $10+ to get to port. During normal times the natural price of oil is ~$60.