Let's just say I disagree completely. And "expectation" has to do with sensibility, which the "housing boom" ain't based on in the least. If that were the case, you wouldn't have families making under $80K qualifying for houses that cost over $500K.
The "ROOT" cause of the whole thing was cheap money. There were other factors that got it steaming further and faster than it should have but without cheap money, they never come into play.