Most Expensive Materials in the World Antimatter $62.5 trillion/gram Californium 252 – $27 million/gram Diamonds $55,000/gram Tritium $30,000/gram Taffeit up to $20,000/gram or $4000/karat Painite $9000/gram or $1800/karat Plutonium $4000/gram Platinum $60/gram Rhodium $58/gram Gold $56/gram