I used to work for a company that did contract work for retail and grocery stores. For the most part, there isn’t a whole lot of direct integration, unless you’re talking about the huge chains and huge suppliers. Buyers make an order, that order gets tracked, shipped, added to inventory, and placed on the shelf.

Walmart is so huge and so nickel-and-dime that I’m sure they track and update prices based on a variety of factors, much like how Amazon does their micro-pricing stuff.