The Verge posted a roundup of browser extensions that track prices of specific products on Amazon and elsewhere, such as CamelCamelCamel, and coupon-finding apps like Honey.
I was always leery of these things as greasing my worst consumerist tendencies, but there's a killer deal on that 3:2 portable hi-DPI monitor that's just perfect for retrogames [Amazon link] and for a hundred bucks and change I am completely slathered.
This was news to me:
For a more hands-off approach to seeing if you're getting a good deal, use your browser. For a few years now, Microsoft Edge has been able to tell you when you're looking at the best price for a particular product from a range of retailers, and Google Chrome can track price fluctuations and notify you when a particular product goes on sale. Edge and Chrome are both available on Windows, macOS, and Linux, as well as Android and iOS.
Corrosively convenient! That said, I would take a Firefox extension over anything a browser maker baked in, not least because of the obvious pressures at play in deals services operated by advertising platforms.