I spent a considerable amount of time putting together a book trailer for PATRIOT'S PRIDE. You can view the result of my efforts below. I do have fun with this type of activity, though I seriously doubt whether it helps to sell books. (Selling books is TOUGH!) Nevertheless, I keep expenses at a minimum by using as many of my own photos as possible. I purchased the video of the sailing ship and the man writing with a quill pen, but the castle is actually Lambert Castle in Paterson, NJ, which I visited a few years ago. I snapped the photo of the antique medical apparatus at an encampment at Sandy Hook last year.
To make inexpensive book trailers, I strongly suggest you walk around with a camera and take photos of everything.
The video was made with iMovie on my Mac.