This is something that I thought of a long time ago, but I think its kind of interesting. Everyone has heard the expressions "A Dog is a man's best friend," "Diamonds are a girls best friend." I think everyone would agree that there is some degree of truth to this. Comparing the two is also interesting and telling, IMO.
A dog is one of the only things on earth that costs nothing to obtain. They are also the only thing on earth that is completely loyal, and gives unconditional love for its entire life.
A diamond is a cold, inanimate object. It is one of the most expensive substances on earth. It has no use and no utility besides its monetary value. It is not particularly rare or precious, rather it is valuable because of the South African diamond monopoly.