Tritium

Tritium is one of the most costly substances that the typical person has probably never heard of but has nonetheless undoubtedly seen, costing $30,000 per gram with costs anticipated to reach $200,000 in the future. Numerous items that glow green are produced, including tritium-made watch dials.

Tritium is an extremely uncommon radioactive hydrogen isotope that does occasionally appear in nature. Similar to how The Fantastic Four acquired their abilities, it must form in the atmosphere after being exposed to cosmic rays. Fortunately for fans of light-up watches, it can also be created artificially on Earth. All you have to do is use a nuclear reactor to irradiate some lithium.

Tritium has been used in a variety of medical equipment, munitions, and other things besides self-illuminating lights. Additionally, it is used as nuclear fuel in tokamak reactors, which are among the world's safest nuclear power plants.

• Cost: $30,000 per gram