I think they do this to game people who use the “rebuy” button without shopping around again. Several times I’ve bought a consumable and when I go back, the exact listing j bought from has doubled in price while many other listings are normal. That’s why I never use the “buy again” section, and if I can afford to wait I’ll find a lower or comparable price on eBay, and hope they aren’t just drop shipping me from a cheaper listing that I didn’t find on Amazon.