8. Mercury — $2,966 per gallon
Mercury is the only metal that remains liquid at room temperature. It is mainly used in the production of thermometers. However, chemical industries, metal production, and agriculture find it useful too.
7. Insulin — $13,100 per gallon
Insulin is naturally made in your body by the pancreas. It holds up the level of glucose in your blood and enhances metabolic processes. Insulin is an essential medicine for treating diabetes.