 The submachine gun can only be sold to other grandfathered individuals; this keeps prices extremely low as the number of permitted licensed individuals is very small and dwindling with time.Eventually, all prohibited guns will be out of circulation.The perceived popularity of submachine guns such as the Thompson with violent gangsters in the 1920s and 1930s was one of the main reasons given for passage of the National Firearms Act by the United States Congress in 1934.