Amazon's pricing I not deterministic. You were likely tracked and information collected to know this was a key item for you. Amazon will market loss leaders to you in an attempt to get you to default to buying on Amazon.

As a former Buyer for a chain of retail stores, the loss leader is effective marketing. I sell you a popular item at or below my typical cost because statistically, a large percentage of customers are making a special trip to my store to buy that product and will make additional purchases at margin. On the wholesale Buying side, these are tools to get past bulk buying tier discounts for seasonal ordering with smaller scale retail.

Amazon is using a convoluted front end system of overlapping product categories and a supposed multi seller listings (despite collectivized logistics and warehousing) on the website you see. This is how they perform price fixing where you do not see honest or straight forward determinism. When you repurchase that same item later without making comparisons, the seller will shuffle so that a higher price is presented.

If you have a well isolated network where device history for social media and internet browsing is totally partitioned from e-commerce you'll likely see even more of the scam. If you see anyone online show the search results and pricing on Amazon, then try to replicate those search results and product price on a device that is totally partitioned from your viewing of the item/price elsewhere, you're likely to find it is not possible. If you then go back to the original device and do the same, you'll magically find the same product and lower price. It is a scam market. This is why they are collecting and paying for all that data about you. We are in an age when automated individual targeting and manipulation is possible and happening. This is why data mining stalkerware is insidious. Scam markets are only the tip of the iceberg and what can be uncovered if you go looking for it. Anyone that has done database or logistics management should have major red flags flying when looking at how Amazon's website is setup. The front end is absolutely untenable garbage for effective logistics. The only reason it is convoluted and search results are terrible is because it is a price fixing scam. The logistical efficiency proves that there is no connection between the front and back end of the site.