De Beers trys to buy all the diamonds they could from very country so they could hold them and sell them for a lot of money.They make us think that diamonds are epensive but if De Beers didn't buy a lot of diamonds they would be not that expensive.
So movie stars singers have there diamonds so they show them and people see them.Magazines sometimes ask a store of dimonds if they could use them or sometimes the Magazines buy the diamonds.