Are Dong Qichang's paintings and calligraphy valuable?

Dong Qichang was a famous painter and collector in Ming Dynasty. His calligraphy is especially good at cursive. Because of the huge number of fakes, most of them are fakes or ordinary masterpieces except the national treasures collected by several famous museums in China. Dong Qichang's paintings and calligraphy have a certain position in the European and American collection markets, but there is also a problem that it is difficult to distinguish the authenticity. Ten years ago, the auction price of Dong Qichang's paintings and calligraphy works ranged from tens of thousands to millions. In recent years, the auction price of paintings and calligraphy works in Dong Qichang has risen to several hundred thousand yuan to several million yuan. However, distinguishing the authenticity is the biggest problem in collecting Dong Qichang's works, so we must be careful!