I think housing is a big part of it. This is an old article, but has been going on for years now.
https://www.wired.co...cities-anymore/
"It's very hard to get people to understand that the affordable housing crisis is not for the very poor," says lawyer Mechele Dickerson of the University of Texas, an expert in housing and the middle class. It's for people with good jobs who are not poor enough to qualify for subsidized housing, nor rich enough to pay the rising housing prices. "A family that makes $100,000 can't afford to buy a house in most US cities," Dickerson says.
I don't know how home prices got this high, are the materials really that high or is it the labor ? If it's in a nice area I've seen lots selling for 80-100K, but this is 10 miles outside the city. Few builders are building smaller homes now, 1200-1500 sf, most I see are 2400-4000 sf. 400-500k is common.
Main reason? ZIRP! Just look at your interest rate on bank CD's & savings accounts. It is way below real inflation rate, and you have to pay tax every year on that measly interest. Stocks and housing? No tax on appreciation of asset until you sell, and house sale is largely tax exempt if it is your main residence.