1. Fishing is difficult: sea urchins live in the ocean and are widely distributed, ranging from intertidal zone, shallow sea to thousands of meters deep sea. Sea urchins will not appear in large quantities. Because of the wide range of sea urchins, fishing is difficult, which increases the fishing cost and pushes up the market price.

2. High-grade food: sea urchin is known as the first-class food in Japanese food, which is delicious and has high nutritional value, and is rich in protein and other nutrients beneficial to human body. Because of people's love and demand for sea urchin, sea urchin has become a high-grade food in the market, and the price will naturally not be cheap.

3. Sea urchins, also known as stinging pots and sea hedgehogs, are spherical in shape, just like purple prickly pears, so some people call them "sea thorn balls" and "Dragon Palace hedgehogs". There are about 85 species of sea urchins in the world, and about 1 species along the coast of China.