If they eventually offer it for $19, it could be they’ve come to their senses. Another possibility is that it’s good old-fashioned price discrimination: You offer it for $49, and sell as many as you can to those who can afford it.
When $49 sales dry up, drop the price and now a whole new group of customers—like you—buy it. If you had offered it at $19 to begin with, you’d have left money on the table from all the people who would have paid $49 but got it for $19.
I bought it and I can tell you they made a killing (I can see how many people bought it as they invite people to a private github repo).
But whatever I'm sure they're making money and are happy.
So you pay for the knowledge you want now a premium fee, but you have to wait a couple of months to have it all?