This is interesting for two reasons. First, Kindle has won the ebook price wars, so far. Kindle ebooks are generally cheaper than other version because Amazon stiff-arms the publishers into going along with their pricing philosophy. Second, it points out the advantage Amazon has over other eReader marketers: they also sell books— a lot of books. This move illustrates that they aren't wedded to a single platform for their future market.
There are also rumors afloat on the web that Amazon will soon support the EPub ebook format on Kindle, which would buy them some good will from open source supporters. As reported by The Motely Fool, it looks like Amazon is making a real effort to put their ebook eggs in multiple baskets.