Starting this summer, the e-commerce giant will offer a 70 percent royalty rate for books published on its self-serve Digital Text Platform, up from the 35 percent of the list price it currently offers. The offer comes with a series of strings attached, but all are aimed at the same goal: Selling titles at the lowest possible price.

This won’t be relevant for most of the mass-market titles, whose publishers negotiate individually with Amazon (AMZN). But it will be relevant for Kindle owners, who tend to be price-sensitive types who flock to low-cost and no-cost titles.

Amazon has two goals here. The company wants to push e-book prices down, which should help it sell more e-books and more Kindles. And it wants to keep business away from a growing list of rivals, which include Sony (SNE), Barnes & Noble (BKS), and, very soon, Apple (AAPL), which will be supporting e-books on its new tablet device.

If the [iTunes music store] was forced to absorb any increase in the … royalty rate, the result would be to significantly increase the likelihood of the store operating at a financial loss–which is no alternative at all. Apple has repeatedly made it clear that it is in this business to make money, and most likely would not continue to operate [the iTunes music store] if it were no longer possible to do so profitably.”

– iTunes vice president Eddy Cue

Not that it would ever have happened anyway, but Apple (AAPL) will not be shutting down the iTunes Store in protest over increased royalty rates paid to songwriters and publishers for CDs and digital music downloads. The Copyright Royalty Board Thursday left the rate for royalties unchanged at nine cents a track, paying no mind to a proposal by the National Music Publishers’ Association that would have raised it to 15 cents–a 66 percent hike.

Seems Apple’s posturing paid off. Said Apple spokesman Tom Neumayr, “We’re pleased with the CRB’s decision to keep royalty rates stable.”