Hey @dorde,http://marketblog.envato.com/general/why-do-we-create-bundles/ is the blog post, I’ll update the link as soon as I can!
Here’s a link to a previous pack:http://marketblog.envato.com/general/the-world-photo-pack-20-photos-for-20/
and here’s a link to some of the authors includedhttp://photodune.net/item/godafoss/2744606 http://photodune.net/item/bear-on-alaska/8254311 http://photodune.net/item/havana-cuba-street-scene/757163
You can find more of them on the marketblog!
As the name suggests, packs are much smaller in price and exposure, and focus on a niche. e.g. Creative Cloud Pack, eCommerce Sampler Pack.