Who is going to consume all the goods that the machines produce? Who is going to buy these, and how?

However much you might not like factory owners, they are not likely to deliberately shoot themselves in the foot.

Like polluting the planet beyond unsustainable levels?

If the great majority of people cannot afford to buy what your machines produce, your market is very narrow. If every producer's market is narrow, there's not enough wealth on it, and they are suddenly poor, too.

This is why most producers, especially huge corporations, go to great lengths to lower prices for another few cents.

No, this is not true, and it's pretty clear everywhere you look. If you're a producer, your first and foremost care is money, not your consumer. Sure, appealing to your customers is a good way to get that money, but it's not the only one. Why do you think that, to pick just one example, companies put so much malware on the computers they sell? Because they calculated that they can do something against their clients that yields extra profits but is not annoying enough for the clients to switch.

Customers are just a proxy for profits.

It's only once you get to the factories building actual "consumer goods" that you see the real concern over "who is going to buy this."

The funny thing is that I spend a lot of time on a forum mainly populated by owners of small factories and I see this come up from time to time. The guys (and they're mostly owners & workers at small manufacturing businesses) are concerned about too much automation having an impact on society, but by far their primary concern is making sure that they automate enough to stay in business and be profitable. After all, it's their kids being able to eat that they're going to be mainly concerned with.

The only inherent character of a market that gets very narrow is that it's narrow. The amount of wealth created depends on, well, how much wealth is produced, not on how many people are available to buy it. If you don't need people to produce wealth, those two things may have no relation at all.

People are making a huge effort here to assure that no, there's no problem. Yet, both Economis and History say otherwise.

If nobody makes anything, no amount of money can buy anything.

If the only people making things are the rich folks who own production capital, they can only trade with each other. If they are not producing the things that rich people want, they can't trade.

Imagine a degenerate world where there are two rich factory owners and 7 billion unemployed people. One rich owner produces food with robots, enough to feed the whole world at $0.01 per meal. The other produces potable water with robots, enough to supply the whole world at $0.01 per cubic meter. Every day, one richie trades a day's worth of meals to the other, who trades a day's worth of water back.

The 7 billion povs can produce food and water, but they cannot compete on price. Even the cheapest pov-made food or drink trades much more expensively than the factory goods. Their problem is that very little that the povs make is worth anything to the factory owners. They, too, would prefer to get their goods from the factories.

Every last pov is relegated to subsistence production, for personal use. The only way out is to produce a trade good or service that a richie would prefer to richie-made goods and services.

In this degenerate world, the most commonly sold service is likely going to be "not murdering you in your sleep and taking control of your factory the next day".

And that is why it is important to care about what people can trade.

Which will be solved by the third richie who has a military drone production and maintenance facility.