30 yuan. According to the relevant data of pickled fish, the cost of a pickled fish is in 20 yuan, so the profit of a pickled fish in 50 yuan is 30 yuan. Fish with pickled vegetables, also known as fish with sour soup, is a classic dish in Chongqing, which is famous for its unique seasoning and cooking skills. Popular in the 1990s, it is one of the pioneers of Chongqing Jianghu cuisine.