The supply of housing isn't a problem in Texas, but "supply and demand" isn't the end of the story. When two Texans want the same house, a bidding war is artificially capped (at, say $300k) because that's all the average Texan can afford. But when a Californian moves in with high net worth and a higher paying job, they can bid much higher, and they don't mind doing so (the mindset I have personally heard from most CA transplants to Dallas is that they don't care if they paid more than the average Texan pays, because at the end of the day they're still paying less than half what they were paying in CA).

And then there's the issue of property taxes. A Texan lives in his nice $250k house and pays $X/year in property taxes. Then someone comes in and buys the house next to them for $400k/yr. Suddenly this neighborhood is now appraised at a much higher value than before, and the Texan's property taxes are now twice as high, bordering on the edge of unaffordable. I've personally seen several people be priced out of an area due to this.