A couple of quick things to note. Teleread points to an ebook price comparison website: http://www.ebookprice.info/. Doesn't look terribly comprehensive, and it's only US sources, but a good idea. Couldn't find Outliers, for example. But the second thing to note is that I did notice Outliers is now selling for only $4.88 on Shortcovers, vs $19.09 when the site launched a month ago!