Earlier quoted context omitted.
I've heard from a friend (in Australia) if you don't frequently buy placement you get bumped, and buying placement can be a losing proposition. They raise the price to squeeze all margin so it's just on the edge of making it affordable. You have to say yes to losing money during the promotion ("you'll make it up with brand awareness!") to claw it back by staying on the shelves in between. Otherwise another brand, or…
Does shelf height play that big of a roll in sales?
Similarly at least one large pharmacy chain supposedly made a significant chunk of profit from charging for catalogue placement.
I don't know about shelf height specifically though, I do know this is an important factor in sales but not sure if there is ongoing 'rent' to pay. There would be a lot of indirect negotiation around wholesale rates that would influence these decisions too.