Its expensive because its rare and elegant. Something that is rare is not as abundant as a simple rock. In economic terminology, just imagine too many people chasing fewer and fewer goods. So obviously the demand increases and if deman increases, prices go up. If diamonds and gold are as abundant like sand and dust, i bet you could have gotten diamonds and gold for free. \nBut I agree with you in food and gold comparision. Food is our NEED and gold is our WANT.