SAN FRANCISCO — The average home in the United States costs around $240,000. But in San Francisco, the world’s most expensive place for construction, a two-bedroom apartment of what passes for affordable housing costs around $750,000 just to build.

California’s staggering housing costs have become the most significant driver of inequality in the state. On Wednesday, California’s governor, Gavin Newsom, mentioned the issue 35 times during an impassioned speech, urging lawmakers to solve the state’s homelessness crisis by building more and faster.

But the vertiginous prices of housing in California show how difficult that will be.

Building affordable housing in California costs on average three times as much as Texas or Illinois, according to the federal government.

The reasons for California’s high costs, developers and housing experts say, begin with the price of land and labor in the state. In San Francisco a construction worker earns around $90 an hour on average, according to Turner & Townsend, a real estate consulting company.