An obvious-in-retrospect insight:
There are lots of perfectly ordinary reasons for land to go up or down in price. A house, by contrast, is a large decaying physical object.
Ryan Avent nods:
High housing costs reflect the high value of access to productive cities — you can’t take advantage of the high wages in Silicon Valley unless you live in a housing unit that provides you with reasonable access to Silicon Valley. When broader shifts increase the economic potential of a place like Silicon Valley, land with easy access to that place also rises in value.