Additionally importantly, some books are simply worth more than others, even in low-volume batches, especially if the books are necessities to those buying them. That's part why textbooks are so expensive, and part why Patricia Cornwell is sold in grocery stores and is perpetually 20% off the cover price. If mass-market paperbacks and even new hardcover books were too much more expensive they probably just wouldn't sell.
I assume that a lot of e-books are the same way, and honestly, they're not priced well, and too many middle-men get in the way. e-books should be the author selling right to me. Call it the exact opposite of the music distribution model; author owns the work and potentially contracts-out editing and marketing, and retains all profit after costs are paid or shares profits as a percentage with editors and marketing depending on the arrangement that they come to.
That Amazon is involved as a middleman is itself a problem. There's no need for the author to sell to Amazon for them to then sell to me when there's no physical medium for e-books, and for traditional publishing, Amazon should just be another traditional retailer, not something special.