I don't think that the price was lowered because the Kindle wasn't selling well; more like they just wanted to sell more units and had finally got production evened out.
Also, some poor wording choices in that interview, which have led sources around the net to conclude that Amazon has only sold 8,000 Kindle books thus far. I think what Bezos is saying is that, while there are currently 125,000 books available through Amazon for the Kindle, Kindle book sales account for about 6% of Amazon's book sales. Not that Amazon has sold about 6% of the available 125,000 books, or only 8,000 Kindle books.
A quick count of all books (not just Kindle books) shows well over 125,000 books in just the SciFi/Fantasy and Mystery sections combined, let alone the rest of fiction and all of non-fiction. Plus a quick check of my Amazon account shows that I've downloaded more than 40 books through Amazon (and more than twice that through other sources, including here), and I've only had mine 3 months and doubt I'm the "leading" downloader.