Expensive. Green sea willow is very precious, about 30 yuan a gram, and the price is expensive. Sea willow, scientific name black coral, is an animal that lives in the sea. This animal belongs to Coral Subclass and is coelenterate. Because it looks like a willow, it is named Hailiu. Sea willow is delicate, tough and shiny, and can be used for processing into various craft products such as pipes, bracelets and ornaments. Sea willow grows slowly and lives in the deep sea 30 meters away. The collection is difficult and the output is scarce, so it is particularly precious.