Francium

The most expensive element on the planet is francium. Prior to the discovery of this incredibly uncommon element in 1939, Russian scientist Dmitry I. Mendeleyev (the guy who created the periodic classifications of the elements) anticipated that it may exist. However, it was Marguerite Perey, a French scientist, who discovered francium in the late 1930s while investigating actinium-227.

You might wonder how such an ingredient could be so costly. The fact that this element's half-life is only 22 minutes adds to its expense. Since one gram of francium has never been seen, the billion per gram is purely theoretical. A cluster of more than 300,000 atoms of francium was the largest number ever synthesized. However, this cluster, or even a gram of francium, would vanish within minutes of being created, therefore it is now useless in today's environment. There are those who are willing to spend billions simply to have a glimpse of this element, and we're confident that scientists are capable of producing it.

To make matters more difficult, just 24.5 grams (less than one ounce) of natural francium exists at any given moment in the Earth's crust. Simply put, this element is virtually tough to locate and even more difficult to manage, making it extremely costly. Although francium cannot be gathered or sold, it is estimated to be worth $1 billion per gram.

Estimated Value: $1 billion per gram