Reason being that for one, Costco was one of the first grocers to start replacing items with Organic alternatives, and in general, they usually demands higher quality goods than other grocers. For example, compare the ingredient list for Delimex taquitos from Costco to your supermarket and it's basically half the size... or Campbell's "Simply" Chicken Noodle soup to what's sold at the grocer - again about half the ingredients. Even those $5 chickens Costco sells are antibiotic/hormone/steroid-free humane-certified Foster-Farms chickens.
Then there's employee treatment. Costco has a long history of being one of the better employers in the country. They pay their employees well, pay for people to attend college, don't require a lot of interaction with irate customers thanks to their no deadline any reason return policy and generally promote internally rather than hiring outsiders to leadership roles.
Compare that to the average chicken farmer who has to buy all of their own equipment that the big companies are constantly requiring them to update at their own expense, raise chickens they don't own like a horrific daycare center at very low return, all while being exposed to chemicals/drugs they're being forced to use and it's kind of a nightmare.
Costco cares about their brand image, their customers and their employees... I expect this will end up being a good thing.