Collecting elements starts off cheap with a bit of aluminum here, a little copper wire there and a lead sinker you found in the basement. Then, as each new slot in your set gets filled in the challenge of finding the next and its price goes up. Then when it gets to the platinum group the price goes waaaay up. Either that or you settle for tiny samples. And this is rhodium, the rarest and most expensive metal ever sold as bullion - and many would say that its exorbitant cost is still undervalued relative to its rarity!

CAS 7440-16-6