A new UserScript plugs an Amazon Historical Prices graph into each Amazon listing page. Possibly of use to book dealers tracking price trends over time, or those seeking to buy a more expensive item (perhaps a few weeks ahead of the possible purchase point, as ‘the countdown to Christmas’ has reportedly started very early this year). One might even use it to spot trends (e.g. the item ‘tends to become cheaper for a short while, once every two weeks’) caused by an AI spotting page-visiting trends among other potential buyers. The script’s code looks clean to me.