I can definitely get that - his podcast is actually pretty legit and value filled. He could totally be lying about his numbers, but after listening to his story, it seems like it took him a few years to ramp up his piano course sales.
I've never read "The Four Hour Work Week" but I always figured that if it was honest, all it would say is "1) write a book about how to only work four hours a week. 2) convince people to buy it. 3) On average, spend four hours a week on this."