Why is lemon caviar so expensive?

This product is made from the roe of the sturgeon fish, a species native to Europe and Central Asia, and everything is a result of its availability, as this fish produces roe every four or five years from the time it reaches the age of 15, making it one of the most long-lived fish, with a lifespan of up to 100 years. It must, however, be slaughtered in order to harvest the roe.