Hunble Bundle says that these audiobooks have a regular retail price of around about $685 (I bet you can find them for less on Audible), but they're letting customers name their price. The minimum payment is 1 cent, though of course you can choose to pay more. And if your payment exceeds the average payment (around $4.30 at the moment) you can also get the bonus titles: A Heartbreaking Work of Staggering Genius, Blood Meridian, and On a Pale Horse.
Content bundles haven't achieved nearly nearly the same popularity as coupon sites like Groupon, but Humble Bundle and others have had some success. Over the past 3 years this site has launched numerous bundles for apps, and they have also from time to time offered bundles of ebooks on similar terms.
And they're not the only ones to offer ebook bundles. StoryBundle, a competing service which only offers ebook bundles, has launched 14 offers since it opened its doors in August 2012. And other sites including BookBale and Fiction Bundle have also jumped in, showing that there is a growing market niche for bundles.