sound engineer or not, you are very wrong, a car can be made to sound "good".
yes, it is a challenge, & yes the car itself is a horrible environment to begin with, but I garentee you there are systems out there that if you could just sit in them & listen for a little while, you would change your mind.
& as far as systems cost... I can buy a whole car right now for $600. yeap, whole car... but then there are people who go out & spend $30k, $40k & $50k & more for a car... why would anyone do that if they could buy a car for $600? why would someone spend 50 times that amount for "the same thing", a car? what? there not all the same?... hmmm