Hafnium is rare and expensive primarily because it's so hard to get it separated from zirconium, a sister element that is chemically nearly identical. Although the two are so similar chemically hafnium is much rarer thus adding to the expense. Due to the rarity and difficulty in preparing the purified metal there are few industrial processes that see a need for hafnium, especially considering that zirconium can fill those roles in most cases. 

Another big chunk of hafnium! This amazing piece of hafnium defies all attempts at description for shape. It looks like a little meteorite. The texture seems as though inherited from the roiling of its absurdly high melting point frozen in time.  Poetic hyperbole aside, this is how hafnium and most of the rare earth metals look like as sold industrially... a look that will quickly grow on the lucky owner of this Lucite cube!

A massive chunk of this rare and dense metal beautifully suspended at the center of this optically clear cube of crystal clear Lucite acrylic.