The monetary density of things

Of course, gold isn’t the only precious metal, or even the most expensive. That “honor” belongs to rhodium, whose price far exceeds that of its weight in $100 bills. There’s an interesting coincidence in this price range: Cocaine is about $50/gram, while a fifty dollar bill weighs about a gram. Even exchange? Platinum is also in the same price range, so you could say that $50 bills are worth their weight in platinum.

http://www.evilmadscientist.com/article.php/density