RE: Ownership
"Therefore the retailer doesn't own the product they've bought?"
I did give you a thumbs up, on the condition of your original thought: you haven't considered that contract law has many levels. If you go to a specific food store, you might want to purchase a certain soft drink. You might find it in a certain aisle, and you pay the food store for the item. The larger stores limit the number of employees to keep costs down. At times you might see a uniformed soft drink representative stocking the the shelves however. They are paid to deliver and maintain the level of stock by the manufacturer of that sweet fizzy soft drink. The food store you are shopping in does not necessarily own the product, but, by contract, shares in the profit and/or simply rents the space to that brand of sweet goodness. There are agreements with many other product suppliers. The specifics of the contracts differ, but are essentially the same where the store does not own the products: it just makes things convenient.
If you think about it, it makes good fiscal sense for the food store since you won't have to roam about looking for the product if you know exactly where to find it every time you visit and in the size of packaging needed. You're in briefly and dropping cash. There is a lot of science in how food stores are run. And don't get me started on the self check-out lanes. LOL!