Like Brian Kelsey, I'm organizing my thoughts for tomorrow's Leadership Austin panel discussion. One of the things that needs to be emphasized in any discussion of affordability is that other large Texas cities have managed to keep themselves much more affordable than Austin despite rapid growth (if not rapid growth in the city proper, at least in the metropolitan area). In 2012, according to the 2008-2012 American Community Survey, the median rent for Austin (city only) was $950, compared to $822 for Dallas, $837 for Houston and $798 for San Antonio. The 2012 one-year estimates show an even bigger gap between Austin and the other three.
There are probably lots of ways to slice this issue, but one useful cut is to look at the age of the housing stock. I've gone on ad nauseum on this blog about units "filtering down" to cheaper markets as they age, and you really do see that in the data when you break out the median rents by age of the structure.
All cities (except, for some reason, the most recent construction in Houston) see rents steadily drop as units age, until 1950 or so. My guess is that the rise in rents in 1950 is in part due to survivor bias (the crappy stuff built in the 1950s was torn down, leaving higher quality units) and the fact that older stuff is located in central neighborhoods experiencing a surge in demand.
San Antonio median rents are far below Austin median rents for each period. But Austin rents for relatively recent construction -- stuff built in the 90s or 2000s -- aren't that much higher than Houston or Dallas rents. (The median rent for Houston's 90's-era construction is within $5 of Austin's median rent).
It's in the older complexes that a significant gap emerges. It's remarkable to me that the 1970's and 1980's apartments in Houston, Dallas and San Antonio all have approximately the same median rent. It's equally remarkable that the Austin median for these periods is so much higher. The gap in rents for 1940's-era construction is even larger, but it's a small share of the housing stock and probably not consequential. But there's lots of housing remaining from the 1970's and 1980's. The reason Austin is so much more expensive than Houston and Dallas is because our 1970's and 1980's housing is so much more expensive than theirs.