The folks that had platinum stocks thought they were going to make a killing when the CAT convertor was adopted. There are other platinum group metals(Vanadium, paladium) used as well. It turns out that the platinum group metal coating on the internal filling of a CAT is very thin. The amount of catalyst in each converter is only about 1.5 grams; about $45 worth. A catalyst promotes a chemical reaction but does not enter into the reaction and is not consumed but it can be poisoned by all kinds of stuff that people dump in the gas tank.