There are no organic listings at all. The only way into Shopping results is via AdWords' Product Listing Ads.
http://googlecommerce.blogspot.com/2012/05/building-better-s...
http://googlecommerce.blogspot.com/2012/05/building-better-s...
>We believe that having a commercial relationship with merchants will encourage them to keep their product information fresh and up to date. Higher quality data—whether it’s accurate prices, the latest offers or product availability—should mean better shopping results for users, which in turn should create higher quality traffic for merchants.