The interpretation of 'luxury' differs, depending on several factors, such as the age group you're in, social class or cultural background. To define the current meaning of the term we need to look at the many meanings of luxury in history and trace those meanings in current usages of the expression.
As we are living in a age of the image, the values of products are influenced by their images rather than by their inherent qualities. How should we define luxury? Is it the image? Is it th brand? Or is it the design or the material? The form, the idea, the illusion?