Extravagencies = cable TV + expensive haircuts + fine dining + designer labels + jewelry + vacations + expensive cars + pets

A luxury is something you didn't need, regardless of the price.

Note that many of these merge into conveniences or necessities, for example haircuts and dining.  A cheap haircut or a cheap meal border on necessities.  Many people feel that a car is a necessity, a few unhappy people feel that a Hummer is a necessity.