One nitpick: maybe it's just the grocery stores near me, but the Pharmacies are almost always located near the front right by where you walk in. Milk is often in the back however.
It wouldn't be smart to put a huge walk-in fridge in the center or front of the store, given the recurring shipments from cold storage trucks to fridge.
... However locally, our Kroger(s) has a small case that holds 15 gallons of milk, and a shelf of common bread up front and center.
That said, I've also noticed that in many larger store they have a small case of frequently bought perishables at the front of the store.
http://www.npr.org/sections/money/2014/07/23/334076398/episo...
Edit: PS: That economist, it's his job to rationalize the action monetarily. I/we/most people realize, if returns could be increeased, hamburger would be in a cooler next to the checkout.