It is now clear that when the landing page simply presents a list of links, the perceived value of the content might not be too high in terms of price perception.
For instance, if it is a set of articles rather than an e-book, the perceived value drops because a visitor is used to have articles presented for free.
It is the same with forums or blogs.
You simply don't usually pay to access these.
On the other hand, e-books can be both for sale and in free access.
Same for videos and audios.
DVD's on the other hand usually mean for sale.
Same with CD's.
The conclusion is simple: if you want to sell a product, it is ESSENTIAL that you present it in a format that a visitor will be inclined to buy.
My feeling is that selling a set of articles rather than an e-book is probably 5-10 times harder.
Beware how you present your content! presenting it in a simple set of links to articles might send the wrong signal and the perceived value of your product might drop instantly!