I generally go to Chemist Warehouse for my scripts, but to be honest I've never really done a proper price comparison with other stores.
If I buy a generic Ventolin puffer, the price always seems to be in the same ballpark regardless of where I buy it from.
For things like antihistamines, Chemist Warehouse is notably worse than most other pharmacies: they only stock brand names. They might have a "Chemist Warehouse Exclusive" box of 240 Telfast or something, but it still seems to cost more than generics from other stores.
Are you suggesting they pay below award wages? Got any proof?