A gram of pure plutonium, for example, would cost about $5,000. [*] As a bonus, plutonium is even denser than gold, which means you could fit almost 300 kilograms of it in a shoebox. Before you spend $2 billion on plutonium, take note: Plutonium’s critical mass is about 10 kilograms. You could technically fit 300 kilograms of it in a shoebox, but you could only do so briefly.
