> Why spend 2-10x as much to live in one of four coastal metros

I think you answered your own question: it’s not (entirely) an economic decision. Weather, culture, nature, civic amenities. There’s a lot in life that money can’t buy. Sure I could own a McMansion on a palatial plot of prairie, but what if the square footage of my house and acreage of my yard isn’t what’s important to me?