The phrase "affluent milieu" is correct and usable in written English.
It can be used to describe a wealthy or prosperous environment or setting, often in discussions about social or economic contexts.
Example: "The affluent milieu of the city attracted many high-end businesses and luxury brands."
Alternatives: "wealthy environment" or "prosperous setting".
The author, whose 15 books include "Not Like Other Boys," a memoir co-written with her gay son, Christopher Shyer, that drew national attention in 1996, fills "Second Chances" with observations about the affluent suburban milieu: "Women and looking one's age were incompatible," she writes.
Ms Brady grew up amid affluent surroundings.
In March, Margaret Talbot wrote in the magazine about Skylar, a transgender teen-ager who grew up with doting parents in an affluent suburb, a milieu vastly more open to his gender identity and decision to undergo surgery than would have been imaginable decades ago.
They mostly portray women, and the settings and dress of her subjects reflect the relatively affluent and educated milieu of which the Rix family were part.
We are, that is, in the familiar milieu of affluent American phoniness, which has served as a scapegoat in a half-century's worth of movies from "All That Heaven Allows" to "The Graduate" to "American Beauty".
The milieu is unmistakably affluent – a chateau in The Unloved, a villa in Swimming Home, and the trappings of leisure and indulgence abound, most noticeably in copious quantities of food and drink.
Tribou, 45, with a mustache and tattoos on his arms that he obtained while in the Marines, grew up in Yonkers, in a milieu distinct from an affluent town of, among others, bankers and brokers.
In one, the cast is largely white; in the other, largely black, though in both the milieu is cultured, cosmopolitan and affluent (Jane Eyre and Smithfield hams cede to Marion Williams and smothered pork chops as points of reference, but the tone remains substantially the same).
Friedrich towered in his milieu.
