I think there is an element of truth in there but maybe it is more to do with the lifestyle and activities that you are engaged in which end up releasing more dopamine. People who live an active lifestyle will get dopamine throughout the day because exercise can release a certain amount. There are plenty of people out there who don't do any exercise but get a hit of dopamine from bad places, like drugs or even food, so it's not always a good thing unless you're thinking about the long term. When you say nice cars, you might be thinking more about an adrenaline rush than dopamine - it'll give you a different kind of buzz but is intended to give the body more of a fight or flight response.