Are commemorative stamps of Japan World Expo valuable?

According to the query of Confucius Old Book Network, the Japanese stamp "World Expo Commemoration" was sold in 2 yuan, and the 20th anniversary of the World Expo "Mawangdui Han Tomb Exhibition" was sold in 80 yuan. 1970 Japan World Expo Commemorative Stamp was RMB 500.00. So I know that the commemorative stamps of the World Expo in Japan are worthless.

1966 May 1 1, Osaka successfully bid for the World Expo 1970. In fact, Japan has a deep relationship with the World Expo. As early as 1867, Japan participated in the World Expo in France, which set off the trend of ukiyo-e painting in western countries. World Expo is a Japanese word pronounced ばんぱくかぃ. If translated into Chinese, it is called World Expo.