"Damn, that books looks awesome!" click buy button to purchase on an impulse "$200 for a book?! Oh, wait, it's for a package..." scroll down to the book "Oh, the book is only $30. I could get it... But would I get the full experience? It says I will... but I'm missing 180$ worth of content..."
And there I am right now, not buying it on impulse, but considering buying it. Knowing myself, I'll forget all about it by the time I get home.