I worked for Frito-Lay for several years and you better believe that's how supermarkets work. More than once I've been called in the middle of the night to a store to rip down an endcap of chips because the store got undercut by another (and in their defense, why would they give us valuable floor space on a promotion that won't sell).

I think though as comparison that the power dynamic is flipped. Exclusivity agreements usually were to the benefit of the store (against big brands at least). But against the small brands on Amazon, they favor Amazon.

Yet that happens all the time. I've heard stories of companies going bankrupt after retail giant X learned competitor Y was selling their product for less, in breach of their contract (feel free to replace "contract" with Amazon ToS).