golden ghetto
n. An urban area with an above-average concentration of high-end stores and affluent housing; any prosperous area or situation.
According to research from financial services firm Experian, Thorntonhall is typical of a new trend for the well-heeled to stick together.

Yesterday, some of the residents behind the high walls and electric gates warned there was a price to pay for affluence, describing their village as a 'Golden Ghetto'.

One man, who asked not to be named, grumbled about the lack of community spirit. He said: 'It is just a collection of big houses behind big gates which people hide behind when they leave their big jobs in the city.
—Iain Fleming, “The Golden Ghetto,” Daily Mail, January 07, 2002
1976 (earliest)
It was once a seaside village of fruit growers, shepherds and peanuts. When rich visitors came, it was no lounge at the yacht club on the graceful sweep of Juniyah Bay or to gamble at the sprawling Casino du Liban. Now Juniyah has become a golden ghetto for Lebanese Christians.
—Barry Came, “The 'Other Beirut,” Newsweek, January 26, 1976