I've been seeing this a lot recently, and I find it really annoying. The reviews are not the place to voice your pricing concerns; they should be used to review product quality. This sort of abuse completely undermines the usefulness of the system.
Of course, Amazon is partially at fault for combining different editions in the reviews.
I have been annoyed at how hard it is to compare different editions of computer books, for example, to decide whether to buy a newer edition or not.
These book reviews are different, though. People are giving 1 star reviews without having read the book, because they don't agree with the price. They are giving 1 star reviews for books that are not available on Kindle. They are not qualified to review the item because they have not used it. Whether or not the complaints are valid, the review section is the wrong venue for voicing them.