Site is https://keepa.com/#! btw
Here in Germany, we once had a hardware store called "Praktiker" which advertised their regular 20%-Off-sales with the slogan "20% on everything except pet food" (the joke was that they didn't sell pet food).
We once needed a very specific type of screw for an old Fender Amp and went to Praktiker when they didn't have their sale on, so we decided to come back when they resumed the sale again, which they did regularly. When we came back to the store, the screw would have been more expensive than before even with the "20% off" (which was a fucking lie). This opened my eyes to all black-friday-prime-day-whatever-day-sales from then on.