The cost of housing rising above median livable wage is not theoretical. We're well past that in some parts of the country.

But does that mean there is too much rental housing available or not enough, versus owner-occupied housing? If you want rents to be lower, it’s strange to argue against an increase in rentable housing.

Rent has also skyrocketed, so your framing as some trade-off between availability of rent or buy does not seem correct.

All else being equal, do you think JPMC building $1B of new rental property to raise or lower rents?

Depends entirely in the property they use to create those units doesn't it? If they demolish 10,000 low end rental properties to build 1,000 high end properties, the answer seems obvious. Equally obvious, if they could create property out of thin air then more supply lowers prices, but property is finite.

If they could buy 10K on-rental-market units at an average price enough under $100K each to leave room to build luxury housing there, it would make a hell of a lot more sense to just continue to rent them.

Well someone is paying it, or else the prices would come down. The middle and lower class are just being pushed out

There should not be megalandlords that can control a significant portion of housing anywhere. "Some people want..." is a lot more theoretical argument than gp. There needs to be limits on the power of landlords. I am curious as to what other countries have done to avoid it. Monopolies are illegal in the US, but it seems difficult to bring anti-trust against landlords.

>Monopolies are illegal in the US

If Comcast isn’t a monopoly for many in this country, I don’t know what is. Serious question: what are some notable examples of the government taking actual action against monopolies in a meaningful way that made them no longer monopolies?

There are no examples in the past 40 or 50 years. The country is infested with illegal monopolies. At this point there really aren't any industries left that aren't completely dominated by 3 or 4 massive companies. This has even spread to industries which have been historically immune to monopolies for various reasons, such as local news, FM radio, primary care practicianers, hardware stores, textbook publishing, car/heavy equipment mechanics, etc.

There are regulated monopolies. (For example, power companies.) They aren't illegal.

There are some business practices that are illegal, but the companies themselves are not.

That's a good point. There are regulated monopolies. But if a monopoly does not have specific legal endorsement to operate (eg NFL, power company for a region, etc) then it is illegal.