Maybe I have a problem with economists, more than anything else. They talk as if all that mattered were growth. Sometimes you need to look past immediate benefits (rich folk move in, drive up prices, buy more products, pay more taxes), and think about the losses: what happens to society when people don't mix anymore—rich live with rich, poor with poor.
The miracle of cities, the energy of cities, the thrill of cities, come from their diversity, not from shiny commercial constructions that cater primarily to the very rich (e.g., New York's Trump Tower and Chicago's 900 N. Michigan). Such luxury super-malls can be (and are) constructed anywhere—in
Cities are special for their ability to contain juxtapositions of glitter and grime, glamour and grit. The glue that holds those contraries together is the people at the middle of the economic spectrum, those who daily traverse the worlds of rich and poor, riding public transit to jobs that pay decently, buying groceries in cheaper neighborhoods, frequenting public parks and beaches, splurging at an expensive department store at Christmas, going out to a fancy restaurant once or twice a year for a special occasion. Without these folks, we eliminate any sort of connection between the extremes, because public amenities tend to deteriorate without their support, enforcing social as well as economic segregation, depriving the poor of hope for a better life, and limiting the rich to a narrow (private) set of activities, interactions, and destinations.
Meanwhile, the middle-class, living in the boonies among the enclaves of the super-duper-rich, become the most isolated group of all, commuting in private vehicles on suburban freeways, never interacting with anyone outside the circles of family, colleague, neighbor, or church. Safety is a value prized above rubies, and the city, with its crime and expense, exists as a place that the middle-class is lucky to be free of; its charms and satisfactions are forgotten, and notions of interdependence, cross-fertilization (of people and ideas), and public good are discarded.
(By the way, this is how Republicans are made.)