"Luxury Car" is a relative term. To someone in a third-world country it may mean anything that runs. To the average person, it may be a car that is a little fancier, bigger, or faster than the regular car. But to the discerning car aficionado, luxury relates to the futuristic designing, high quality and outstanding engineering.
Some late model pre-owned "Luxury Cars" are great bargains, particularly when thinking of advanced engineering features. It's possible to drive a 4 year old Mercedes, Porsche, or BMW for half the original cost with careful shopping. The car still has the same luxury features, high quality, and outstanding engineering as it had when it was new. The car will depreciate far more slowly than it did the first four years, and you may even sell it for as much as you paid for it - in effect, driving for free.
However, if you decide to purchase a new luxury car, purchase one in which the manufacturer is showcasing new engineering innovations. This will insure that the car remains technologically advanced for the immediate future and will help maintain a higher than average re-sale value. True luxury cars are those which are not just called luxury cars because of fancy names and more chrome and trim packages, but those which are truly outstanding in all aspects including high quality and advanced technology.