How Effective Are Video Book Trailers?

Shades of Milk and Honey author says video book trailers are a useful tool to be able to send people. No good metric exists right now at least as far as I'm aware for how effective they are, she adds. To have a video professionally done is going to cost you about $250 per minute minimum. Most trailers that I hear are costing around $1,500, $2,000 for a bare minimum on a book trailer.