Unfortunately, it's not actually obvious. There are heaps of people, even and especially in the most expensive housing markets in the US, who will outright argue that supply and demand doesn't apply to housing.
The problem with roads is that cars are really really inefficient and drivers don't have to pay for the road, so a driver can extract government subsidies by driving more.
You run into the same problem with free or heavily subsidized public transit. The trains were crowded in Germany when the government instated a temporary 9€ ticket for all public transit (buses, subway, tram, regional trains, etc) in all cities.
It is more complicated than that, for sure. I definitely pay for the roads in my city. And I pay for the mass transit in my city despite almost never using it.
It does not seem controversial that if you raise the cost for something, less people will make that choice. That does not mean that the underlying demand actually did not exist to begin with. If you made the cost zero, you would find the real demand.
Yeah it seems like there is a widely held belief that people are freeloaders looking for any opportunity to take something they perceive to be free, so they go do things they would not otherwise do. A much simpler explanation is that when the cost is low they do what they wanted/needed to do, and when the cost pushes the ROI too low they do without something, or find a workaround. The demand is still there, just unmet.
