Hello Victor,
I will like to argue from another point of view entirely. It will like to say, it also depend on who promote your product/service. There are some trusted name (I will not mention names) in IM niche for instant that whenever they recommend a product, the subscribers will always buy regardless of how good or bad the salespage look. This is because they have built trust over time.
Therefore, One might have the best sales copy in the world, if not marketed properly through the right people and the right channels, it will just become another free online brochure/sales copy sample other people use as a model to write theirs.
Hope that sound reasonable!
Warm Regards,
Olusegun Balogun