How do you distinguish between a "manufactured desire" and a real (/non-manufactured, whichever terminology you want to use) one? If I saw a commercial for a p

How do you distinguish between a "manufactured desire" and a real (/non-manufactured, whichever terminology you want to use) one? If I saw a commercial for a pet rock, and decided that I wanted to buy one, what's to say that this desire is not real?