For quite a while now, I have been careful when buying from Amazon, especially when buying stuff that doesn't cost a lot. Amazon was always cheaper on a lot of inexpensive mundane items to the point I always just went to Amazon, bought the thing, and knew I got a good deal. At some point, maybe because of all the third party sellers, those prices started to fluctuate a lot.
Let's just say as an example I want to order a cleaning product like Soft Scrub. I might go to Amazon and see quantity "X" for $15, but then find it for $5 at Walmart. It used to be that the Amazon price on that was always competitive, if not cheaper, plus it came to my front door. I can't count on that anymore, to the point that it might be double or more at Amazon.
Same with stuff like water filters, vacuum filters, toothpaste, whatever. I still find Amazon prices on those things that are competitive, but I no longer trust that they are. I always verify. I don't find such discrepancies with higher dollar items. Whether a TV or a red dot sight, Amazon will be somewhat competitive.