Each phamacy chain has employees who are called buyers. These people then negotiate with the wholesaler. For example walgreens needs to reup there supply of stomach acid meds the wholesaler gives them a break if they fill generic scripts with there brand. that is the first level.

second level-ins company A sends there contoler to watson brand meds and asks for a deal. they get it it. so employee gets break when generic watsons are given. Problem Mallie wants a piece of the action so they go to ins company and offer a better deal so now all employess who use ins company now have to use mallies to get generic rate.