It is my belief that rent price scales with the leftover income people have after they've paid for other necessities. Ie if you're from a poorer country/area then things like milk and gasoline will cost a similar amount (maybe 2x difference), but rent will cost a lot less. As people in a country get richer they start paying a larger and larger share of their income as rent of various forms.
Even the US has places with cheap rent/housing. The downside is that there's no (well-paying) work nearby.
It’s true that average rent prices are regional and poorer areas have lower rents, but that doesn’t tend to make much difference in urban areas and large cities where the majority of people live now. Why do you feel that rent scales with disposable income? Economists generally say the opposite based on housing being a core necesessity; that people pay rent in proportion to their income, and only what’s left over the the disposable amount. That’s why we have the 30% rule, for example.
You’re technically correct, btw, rental housing is a market and is subject to market forces, meaning what people are willing to pay. I’m just not so sure about framing rent as being lower priority than other necessities. And rent prices have been increasing faster than other necessities, and faster than income, so that might be a confounding factor in your argument.
Still, my initial reaction above is due to the fact that in the US and in Europe in most large cities, the average rent is north of $1000/mo.