Imagine you buy a piece of land for $100,000 with the intention of developing it. Until the property is developed and sold, you have numerous carrying costs (taxes, insurance, debt payments, etc.). In California, your annual carrying costs may easily be $8,000-$10,000 per $100,000.
If it takes you one year to develop the property, you need to sell the property for $108,000 just to cover the carrying costs (i.e. this doesn't account for the actual construction costs or selling costs). If it takes you two years to develop the property, you need to sell the property for $116,000 just to cover the carrying costs.
Keep in mind, the time to develop isn't idle time where the developer incurs only carrying costs. It's endless drafts, consultations, and meetings. It requires actual money to be paid not only to the city, county, and state, but to architects and planners and contractors to comply with increasingly byzantine and mercurial requirements. The longer this goes on, the more money a developer has to spend.
The longer a developer is forced to carry the property, the more they need to charge to recoup their investment. Since no one is going to develop property without anticipated profit, this means prices necessarily rise.
Ideally, yes. In practice, no. Capricious zoning and development regulators are on the HN front page at least weekly.
From the article:
"These energy rules reflect an important priority for Californians, but they contribute to staggering construction costs and, in turn, higher house prices. Affordable housing builders spend $400,000 per unit, on average, for new housing in Los Angeles, more than any other city in the country. State energy standards contribute to this cost."
As you say, labor seems like a much more significant factor. And restrictive zoning and NIMBYism even more so. But restrictive zoning is a sensitive topic for conservatives. Conservatives seem to be against regulation except when it's used to preserve the "character" of existing neighborhoods--not to be confused with historic preservation, which is bad restrictive zoning. Direct regulation is a more convenient target, ideologically. Likewise, I often hear conservatives lament the cost of labor but they're walking on glass by suggesting that working-class voters should be paid less.
To be fair, progressives make the same mistake of assuming new housing should be built for the poor and working class. And NIMBYism knows no bounds. Indeed, it was progressive efforts to "empower" communities that opened the doors for NIMBY obstructionism. It's difficult to devise a political mechanism that won't ultimately benefit the rich and powerful more than the poor.