Well, "common convention" dictates that yes, if one is driving a "nice car", chances of a carjacking transpiring is higher.
But...I've witnessed people getting carjacked while driving an economy car.
Some criminals do believe that a driver of a luxury vehicle is going to put up less of a fight. It also depends on the driver in question. A case could be made for either side though. Also depends on where this crime would take place.
Florida for instance. Here, as You probably already know, without a CCW, one can have a gun in one's car under the private conveyance laws/rules. . I have family here that has had to deploy their pistols to prevent them from being carjacked, mugged, etc. The crime was prevented and in some cases, when apprehended, authorities placed the would be robber under arrest. I'm not saying this is an end all, be all to the cessation of crimes such as these. However, after talking to one of My uncles who is a retired Miami-dade LEO, He's stated that it sometimes makes criminals think twice.
Now take My recent former city of residence, NYC. Criminals have it much eaiser up there. They know that their "mark" is most likely going to be unarmed. No laws like Florida. Thus, making it a very easy crime to commit. Chances are actually higher that the criminal will have an illeagal firearm in the commision of said crime.
Earlier, when I mentioned that even economy cars are taken, here is a recent news story on the subject:
Queens woman carjacked.
Even worse, She is an Elderly woman. Sad news.
What really kills Me is what Her son said. His fatalist attitude is all too common in NYC. Pitiful.