Good info, I'm surprised that haven't figured out how to account for coupons. Seems very feasible, especially considering the army of people with extensions installed.

It's available in the US as well. It's replaced my usage of Camel^3.

Iirc the built in history doesn't take into account games like having a perennial 40% off coupon that gets disabled right when a "sale" starts

Yes. In the UK they go up a month before, because we have consumer protection laws that required retailers of e.g. white goods to have maintained the higher price for any announced discount for at least a month. So you knew that sellers thought there would be (at that point unannounced) Deal Days, because the prices of some things went up 20% back at the beginning of September.

I had ordered a new wireless charger about two weeks ago (without Prime). a day or two before it was meant to be shipped (about a week before Prime day), my order was cancelled "due to lack of stock". I go to the original product page and what do you know, it's in stock but $3 more expensive. Looking again today, it's on the Prime sale for the old price.

Scummy behaviour at best, and illegal at worst.

There's https://camelcamelcamel.com to check how prices developed.

There's still the possibility of shenanigans with different models that can be overpriced for long so they look like a good deal when they get a normal price

the software is running at 1/1000 the capability of the hardware.