For people who use Amazon (most people?), I recommend using a free Chrome extension called Honey (
https://www.joinhoney.com/) as it can show you the price history for the item on Amazon that you are viewing to know if you are getting a good price and jump on it or if you should wait, and it can also notify you if the item you are watching drops below a price that you set. Also it collects discount codes and can test them for you to see if any of them work... that works occasionally too. No commission for me, just a satisfied user.
Here is the price history for the item under discussion:
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