For book/ebook authors, publishers, & self-publishers
I’m not sure about book trailers. Most only seem to get a few viewings if you look on the ones displayed on this site. So even a conversion rate of one in a 25, which may be very generous they have little value against the cost, unless people are watching in big numbers.
My own videos, which I made myself, seem to range from 45 to 280 views on you tube and similar from my own site, with daily motion and others accounting for about 500. That would mean on the one in 25 conversions, 40 people may have purchased a book. If you buy a trailer then even with a 1000 views it’s not paid for the trailer cost.
Here is one I made myself. It cost nothing to make, nothing to put on the web, so any return is a bonus. So the moral must be, do it yourself, or don't expect a return.
I didn't pay anything for my trailers. I'm fortunate to have an artistic family. My husband put them together and my daughter did all the character art, I supplied the narration and we did the music. On this 1st video I'm climbing toward 1000 views. I have total of 5 with more on the way for each book and all homemade.