Why is an
ounce of gold worth $1000? Because that's what people will
 pay for it. It has no inherent use; you can't eat it, you can't live
 in it, you can't keep warm with it. 
 On the other hand, it resists corrosion, has good electrical and
 thermal conductivity and is quite ductile.  Not many metals share the
 same characteristics.  So it does have inherent use.  My wife plays a
 flute that's made of a gold alloy and she says it lends a warmer tone
 to the sound than does silver.
 But then, polonium is even more uncommon than gold but I wouldn't
 want to make wearable trinkets with it unless I were a sociopath. 
 
As far as commodity values of metals, isn't the peak rhodium or iridium
or something like that?
Peace...  Sridhar