Okay, I
think I've sorted out what he means by this:
Your opinion about design pleases you. That's nice! That's sweet.
My opinions about design actually effect what cars are bought and driven!
What I
believe he's saying is, that
you, poor peon that you are, can't actually afford to purchase a BMW, so your opinion doesn't effect what's "bought and driven"...
But because his wife allows him to give his opinion when
she is buying a BMW (obviously he couldn't afford one himself on his part time lab assistant salary) that means
he is having an effect on what is "bought and driven"...
This of course assumes that she actually gives any weight to his opinions, which of course is a highly questionable assumption...
I believe
that is the boorish point he is clumsily attempting to make, rather than the bizarre claim that the design team at BMW is consulting him for advice on their car designs...