Ramit, much of the skepticism comes from the secretive and untracked nature of these types of sales. Take the original article, for example, with the unsourced "I know a guy who makes $5 million+ per month" quote. The comments here on HN are full of people who insist it is possible and a few people who "know what ebook he's referring to" but no one will provide any concrete references. In fact, no one has even pointed out what the subject of such an ebook would be, or what demographic would purchase it.
Without any concrete examples, I'm inclined to assume that it's some variation on the "get rich quick" scheme. This makes the numbers even less believable, as the ebook author has even more incentive to claim extraordinary sales numbers. No one wants to buy a get-rich-quick book from someone who claims to sell 10 copies per month. If an author claims to rake in $5,000,000 per month, then people are going to want to hop on the bandwagon and buy his ebook.
Without any concrete examples, I'm inclined to assume that it's some variation on the "get rich quick" scheme. This makes the numbers even less believable, as the ebook author has even more incentive to claim extraordinary sales numbers. No one wants to buy a get-rich-quick book from someone who claims to sell 10 copies per month. If an author claims to rake in $5,000,000 per month, then people are going to want to hop on the bandwagon and buy his ebook.