Nashville did an excellent job of leveraging its mild climate & music/arts scene into a booming economy. While it the city's infrastructure is terrible, its narrow streets & even the inner loop's highway barrier have - thus far - been working in favor of Nashville. Narrow streets slow traffic, making things feel pleasant for pedestrians & adding to the quality of the urban environment. The inner loop works with those narrow streets to create a development boundary.
Property values are very high in Downtown Nashville for at least three reasons that I see:
The arts scene & all of the economic activity that brings.
The narrow streets inadvertently provide a decent experience for pedestrians, which turns out to be an inadvertent value add for residents.
The infrastructure makes getting between Downtown & the rest of Nashville so difficult that a lot of high income folks with business to conduct Downtown will just live Downtown (or adjacent to Downtown)
I don't think that Nashville's poor infrastructure will slow down migration from wealthy coastal city folks. Property values in Nashville's urban core & in Williamson county will continue to climb for the foreseeable future. But that's not to say that Nashville won't have problems. By not acting on infrastructure issues, I think Nashville has been setting itself up to have massive wealth inequality issues, similar to that of the Bay Area. Home prices in nice places will keep climbing while non-desirable places to live will collect all of the people who can't afford $1M homes: from service workers to folks who struggle with mental illness or addiction. Many will be priced out of Nashville altogether, which has already started happening. Before long, I think Nashville's only middle class will be people who work(ed) normal jobs & were lucky enough to buy property in a nice area early on.
Even if Nashville's existing infrastructure were good, it wouldn't be able to build out forever. The City is in a pretty geologically significant river valley, where developable land is surrounded by steep hills and peppered with floodplains. Then there's the huge chunk of this river valley that would be a great candidate for development, but it's full of Williamson County's estate & ranch style homes. Good luck making room for the middle class there.
Nashville and Tennessee should've invested in infrastructure early in the way that Salt Lake City did, but that obviously didn't happen. I don't know if there's a way to prevent the aforementioned wealth disparity issues without re-dedicating a significant amount of ROW in the metro area to transit. The residents of Nashville consistently vote against any infrastructure that isn't for cars, whether it's transit or "just" infrastructure to prevent homes from flooding. I think the upcoming transit referendum has a good chance of passing, but it doesn't go nearly far enough.
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Now let's contrast Nashville to the two cities in the Midwest that have been growing very quickly in recent years: C-bus & Indy. These cities have much better infrastructure than Nashville AND they don't have significant physical barriers preventing sprawl. The effect is that property values in C-bus & Indy don't reach the same extremes as in Nashville. Simple supply & demand. The upside is that there is no real threat to the middle class in C-bus or Nashville, and there probably never will be. The other side of the coin is that C-bus & Indy are destined to be insanely sprawling cities; it will be a while before it makes more sense to build 30 towers in Downtown Indy or Cbus than it does to just build another ring of suburbs. It's... not great.