If you live in a magical fairy world where supply and demand are fixed, sure. In the real world, prices going down 10% leads to a surge in demand, and so you can fill more of your units. This leads to either equal or increased revenue, for the same construction (flat cost), which actually yields higher margins. This is why developers are usually concerned with occupancy rates, and prices are more a concern for homeowners.

There are only really 3 scenarios where prices are low and demand is low:

[1] There is a dramatic surplus of supply, in which case if a developer is trying to build they've not done research and probably should not get financing

[2] There is some other factor (usually high crime) in which case again, developer should do their research, and the market is operating fine

[3] You are developing super early and operating within incentives offered by the city, usually tax abatements, which drive down the carrying cost and make it a better investment.

Also important to note that in scenario [3] a smart developer will slowly release inventory to restrict supply to meet demand, and as demand grows, release more inventory at the newly raised price, continuing to do so as long as the tax abatements advantage the strategy. This is common in successfully developed areas e.g. Jersey City, and is fine as long as broad scale collusion doesn't occur

Can you define razor thin? Grocery stores have very small margins, as little as 1%.

Homebuilders make at least an order of magnitude more on a very expensive item.

For nearly every homebuyer, a home is the largest purchase they will ever make and the bulk of their net worth. It needs to be a good long term investment that at least reasonably paces with inflation, otherwise you are losing money by buying a home and everyone has to rent and then you have feudalism with extra steps.

The good news is this is totally fine with keeping cost of living under control and overbuilding, because prices will go back up over time. Most people aren't going to own their home until the 30 year mark so it really is a much, much longer term investment than anything like overbuilding or other factors can reasonably affect.

The problem is really that people started seeing 2x-10x returns on homes and started treating that like the norm. That is not a 'good investment' that is a 'money printer,' and in most cases the government does not want to safeguard that behavior, but it's hard not to when those same people panic like crazy if their home only goes up 2% in value in a year or, god forbid, decreases in value for a year.

There is really no good solution to that mentality, if there really was one then Wall Street would have uncovered it ages ago to get more people into long term ETFs.

They can throw up 8-10 story apartments in Tokyo despite land being very expensive because they tear them down and rebuild them after 20-30 years. Also, Tokyo outside of a few areas isn't that tall, it is definitely dense, but 3-4 story tall building dense (those homes are also torn down and built anew ever 20-30 years, so construction buzzes in Tokyo).

It would be better if you considered new actual living capacity in Tokyo rather than just new constructions.

Why are you accrediting Houston to the free market rather than Tokyo?

Have you seen Tokyo?