Those are all pretty terrible (those Circle of Seven ones as well).
Aside from those sponsored by literacy programs, and one from a larger publisher (the one for The Book Thief), there's only one trailer I can remember that made me at all interested in reading the book.
It was for The Body series, a genre I'm not even normally interested in. It was produced amazingly well, with stellar graphics, image, sound, plus it had this great fact tidbit presented by an expert.
Outside of writers, I've yet to find anyone who's even aware of book trailers. If you're hankering to do one for your own entertainment, then by all means do so. I think there are far more effective ways to market your book.
(And this is coming from someone who does video for a living.) If the video isn't top notch, no one but your friends are going to sit through it. I've politely watched several that were awful, from small press friends, to anthologies that I'm part of. It's a different animal, even to write for - and why make the book look terrible? Honestly, it's what most of them do.
(AuthorHouse was soliciting video artists a few months ago - their offered budget went from $2500 to $250 if you answered the ad...I do wonder how much they're charging the writers.)
Having produced other types of shorts - a decent short will start at around seven thousand dollars and go up. More for GOOD animation. There are plenty of book trailers that are full of bad animation, and lousy artwork. That could be why they won't sell the book.
Now, if you want to sell yourself (not as dirty as it sounds), a one minute mini documentary about you might not be a bad idea. Show people what an interesting person you are, get them to like you, and they might show an interest in the book. If your area of expertise coincides with some aspect of the book, even better!
And it can be oblique - perhaps you worked at a four star resteraunt in college. In your book, the murder happens in a resteruant. Talk a little about how tempers and tension run high in the kitchen, and how that could lead to violence. Or something. You get the idea.
Or, if you're wealthy, hire a company that knows what they're doing to make the trailer. Otherwise, you're just throwing money away.