I guess - I'm not understanding what you're talking about (I didnt see any place where he stated that his LFS said anything like that - i.e. maybe I missed it?). Keeping a tank at a lower salinity would cost the store money - because they were selling less salt over time.
I was using the word "sell" as a synonym to the word "convince." For example, if the LFS thinks it is so important that a fish be kept at 1.024 SG because of O2 concentration vs 1.026 SG, they will try to convince you of anything.
Maybe its a regional expression like coke or soda or pop.
I never mentioned anything about making or losing money.