In some places bird saliva is an expensive delicacy

Bird’s Nest Soup is often called ‘The Caviar of the East’, as it is both extremely rare and extremely valuable, only eaten by the richest people in the fanciest of locations. What makes Bird’s Nest Soup so interesting is that the main ingredient in it is made from bird saliva. The bird in question, the Swiftlet, makes small nests out of twigs and its saliva. These nests can cost anywhere between $2,500 and $10,000 per kilogram, which results in single bowls of soup costing an average of $100.