Let's not pretend that we are babes in the woods, with glistening eyes just opened to the world, trying to decide for ourselves what a "luxury car" really is.

This is a well defined market segment for suppliers and consumers alike. It is a term of art used by industry analysts, investors, producers, and car buyers. Don't create your own definitions or philosophical musings about "what is, luxury, really?". If I say I am going to buy a junk bond, you don't need to start questioning "what is junk? All things are needed in life. One man's junk is another man's treasure", etc.