Actually, I think it's usually a fair guess when (as with FF), a sample of the movie is offered. If that's really boring, then there isn't much hope for the movie.

On the other hand, the trailer I saw for "The Incredibles" was a dreary bit of Mr. Incredible struggling into his superhero suit. The movie was much better than that.

You can't buy brains. Money might improve your odds, but it's no guarantee. I bet it's entirely possible to spend the usual amount or more, and still get a marketer who has a fit of cluelessness at the worst possible moment for making your trailer.