Look at the quality of some of the content; extremely poor, but the cost does not reflect. The word scam may be too harsh, but I can't tell what it may be like when you pay for something and feel ripped off. Most of such content I have noticed, are generally referred through reddit via free coupons. But that does not negate the fact that they are being sold.
The Udacity content is all free, or as free as it is on Coursera and edX. You pay for additional stuff like code reviews, but the lectures and quizzes are all free.