I have detected error in defination of luxury. The word luxury in my view means pure luxury and i see a mixup of all types of cars sitting under luxury bracket.
Usually luxury cars have extra soft damping long travel suspension, additional material inside to reduce noise, a whole pack of luxury items for the use of passengers, sufficent displacement engine to carry additional load, sufficent leg space for all passengers. Limos carry additional luxury items for passengers.
The luxury word used by OP is misinterpreted many times in the thread