I have lived in Austin for a couple of years, and also lived here (and owned a house here) about 8 years ago. The cost of homes here has gone up tremendously since then. I was shopping for a house a few months ago, and was simply unable to buy one; those in my price range wouldn't accept my offer because it wasn't an all-cash offer (despite being $5000 or more over the asking price). Investors paying cash are buying aggressively here, driving up prices. Rental rates have risen at an even faster pace.
Certainly, it's cheaper here than in Silicon Valley. Five years ago, I was paying $2145 a month in rent for a house a couple of blocks from downtown Mountain View. Today I'm paying $1690 a month for a house quite far outside of downtown Austin and on the east side; renting in downtown is not an option, even at $2000+ a month. Apartments are somewhat cheaper, and buying a house is still notably cheaper than Silicon Valley, but the gap has been closing rapidly.
In short, Austin has grown incredibly fast in recent years, and the real estate market hasn't been able to absorb that growth in anything like a reasonable manner. So much so that I'd be shocked if the graphs in this article still reflect reality for Austin.