Question

"the law of demand does not work all the time. for example, think about the demand for luxury cars (e.g. bmw, porshe, etc): demand for those luxury cars increases when the price of the car increases."

Answer 1

The statement above is TRUE. This is because luxury cars are superior goods.
Superior goods refers to those goods whose consumption increases as their prices increases, that is, the higher the price, the higher the quantity demanded. This type of goods are usually scarce and and they have high prices. A good example of superior good is luxury car.