> If landlords in Austin tried to raise rents then people would go to Kansas City or Buffalo or Louisville.
In the real world, most people can't just relocate their life on a whim, and the majority of citizens are more-or-less locked into a specific area for long periods of time, for a whole bunch of reasons. (Employer, Spouse, Children, Extended Family, Networks, etc)
It's not impossible to relocate or anything. But most people can't do so, and the few who can usually can't do so easily. It's not like window shopping for cars or clothes, these markets are effectively soft-Monopolies.
If landlords in Austin raised rents, most people would just have to eat it, unless it got to dystopian levels that forced them to relocate.