In Europe there’s a law that forces stores (online but also physical) to post also the lowest minimum price in the last month.
So it would be
€199€64 (lowest price in the last 30 days: €39)Amazon US doesn’t do that, but they do show a “lowest price in 30 days” badge that is actually truthful (appears when the item is on sale and the sale price is the lowest in the last 30 days). Of course, there’s some sellers that game it by increasing their prices over 30 days before Prime Day.
Prime Day is just Black Friday in July. Amazon is trying to get rid of old stock.
If you have an idea of what you want before the sale starts and know how much the standard price is you can still be lucky and get a good deal. You just have to be careful not to get sucked in to a non deal.
For example, I was looking out for an Apple Watch. There is a good sale on them but they only have a limited set of body and strap combinations. I don’t want any of the straps on offer so it negates almost all of the discount as I’d be paying £50 for a strap that I wouldn’t use.