www.gandul.ro/actualitate/cel-mai-scump-metal-lume

Californium-252 is the most expensive metal, priced at approximately $25-27 million per gram, making it about 200,000 times more costly than gold. This synthetic radioactive element is produced in small quantities in nuclear reactors and is not available for commercial sale by the kilogram. Californium-252 is valued for its neutron emission, generating around 139 million neutrons per minute, which is crucial for nuclear reactors and industrial imaging. Its applications extend to cancer treatment, where its neutron emissions target cancer cells effectively. Despite its high cost, it is produced in limited amounts in the U.S. and Russia, with stringent safety measures for transport.