He didn't just trade; he sold knowledge. His courses were expensive then (hundreds of dollars when that was a month’s salary) and are expensive now.
Gann did not have one single course. He sold several at different price points (from $500 to $2,500+ in 1930s dollars). The main authentic ones: wd gann courses
W.D. Gann courses are educational programs that instruct students on how to use Gann's methods to analyze and trade financial markets. These courses cover a range of topics, including: Short piece on W