I think they key is that in your example, Cosco/Walmart was "buying" from the company and is now "buying" from a competitor. Google's typically not "buying" fro

I think they key is that in your example, Cosco/Walmart was "buying" from the company and is now "buying" from a competitor. Google's typically not "buying" from anyone when they choose who to list on their pages (only "selling" exposure, in cases of paid advertising).