Book trailers (like movie trailers only for books) seem to be the new hit thing.
Standard price right now is $50 USD plus expenses (like paying for music or photography rights, should the need arise). You can see samples at this link or scroll below.
Another word about book trailers... My philosophy is that promo videos for books should be like promo videos for anything else: short, snappy, and to the point. My promos tend to be between 30 secs and 1 min long, because I don't believe people want to watch anything much longer than that. I am pretty much your average viewer: I have a short attention span, and don't stick around for things that are boring. My apologies to fellow authors who make trailers, but I've yet to sit through an entire five minutes of video showing a book's blurb.
I also use royalty free music and images, so I can guarantee everything is legal and they won't be pulled from YouTube.