About 2 or 3 years ago I did a post of how powerful the traffic from YouTube is converting. Visitors from YouTube convert by more than 5 percent if you bring the right video to the right product.
Marlow started to sell his bass lessons a few weeks back here and I see extremely targeted traffic from YouTube for his files.
His beginner lesson is posted free and he motivates his buyers to buy additional tabs and documents around the basic free lesson.
See his bass lesson on YouTube and note the links in the description.
If you search for tradebit on YouTube, you will find a lot of crap products that people hope to sell quickly. But the secret of success is: (tata, drum roll) quality!
People tend to buy more and quicker, if you post a video that actually HELPS them for free. They buy the additional stuff to dig deeper and they really mean it then!
So in order to pump your sales, if you have a series of 10 videos: post 5 for free and ask your viewers to get the rest for a small price, including additional material in PDF, etc. That REALLY is the secret. Everyone looking for the quick dime will just fail!