Here is an explanation, from the New York Times, of why a family of five—having bought a Brooklyn townhouse for $1.7 million, renovated it top to bottom for an undisclosed amount of money, and seen it burn down in a construction accident at the very moment of completion—decided it would be necessary, as a next step, to go shopping "in the $4 million range" for a roomy apartment in downtown Manhattan:

They wondered about rearing young children in a four-story house. "There would have been many falls on those stairs," Ms. Wong said.

Imagine: the terror of raising children in a house that has stairs in it! You'd have to be crazy! And so hyper-protective parenting chases hyper-entitled spending in a delightful outward spiral of money, with excess redefined as necessity. A luxury item—a home in New York City big enough to have stairs—becomes a problem, to be solved by an even higher level of luxury. Next step: another townhouse, but with an elevator.