When it comes to my book trailers, I make my own on Windows Movie Maker.
It's all rather simple and probably looks like it's done on the cheap but as I'm no expert and this, along with my self-publishing guide, didn't need an overly done trailer to market it.
I made it so you could read the book blurb and see the cover, nothing fancy needed.
If you know someone who can make it on the cheap or for free then make trailers for your books if you write. They don't have to be masterpieces, just buy some snappy music, get some snappy pics and away you go.