Given that Gage Skidmore owns all rights to the photos, and that Priceonomics apparently had contacted him for this article, it seems quite plausible that Gage allowed the photos to be used outside the CC license.
Furthermore, one might argue that showing photos in an article about them is covered by Fair Use principles. In this case no reference to license or source would be needed.
Furthermore, one might argue that showing photos in an article about them is covered by Fair Use principles. In this case no reference to license or source would be needed.