I do not think you can compare the two, even if GM were to sell it for 100k more and do whatever else it needs to to obtain that price in the market.
GM = lacking in the ability to create a quality car.
I have owned a number of american cars and the Aussie equivalent of GM (holden) they are pieces of shit, yet I love them
Having said thta - merc / porsche / bmw = whole different type of car.