Your initial claims here don't follow: Lower prices certainly do have an affect on author's income. Authors receive a royalty based on a wholesale price, which is (normally) directly related to the price you pay as a consumer.

Publishers' and authors' interests are fundamentally aligned. Volume and pricing affect everyone in this equation. It seems like they should be the ones discovering and ultimately setting the right price/volume ratio, not Amazon.

(I have no idea what you're driving at in your last two sentences.)