My girl was looking for a dress for Halloween. Yesterday she found one on Amazon for € 35 and put it in the cart, but did not buy it. Today she looked it up again and it was € 50 so she asked me to look it up with my phone with my Amazon account - it turned out to be € 23 for me, less than half of what it’s for her!
Yeah there’s a few reasons why the offer that wins the buy box (the term for which merchants offer is shown to the customer prominently) and is complex, but I wouldn’t consider it particularly sinister or designed to mislead. If one person has prime and the other doesn’t, it might weight more towards a prime offer which may be more expensive, a price from a merchant may have changed, or gone out of stock.