How are graded cards correlated to sealed box prices?

Hey guys,
this is my first post, so forgive me if this is in the wrong section of the forum. (First time posting in a forum in general as well)
I started getting back into graded card collecting in the end of 2019 with the intention to complete a few sets (with fossil my first goal) and keeping them over the years.
Of course everyone witnessed the current hype and spike of prices especially of vintage sealed product.

My question, as in the subject title mentioned, is how the prices of sealed boxes and graded cards are correlated (in the same set).

For example I believe WOTC box prices will go even further than that and increase in value tremendously. So does that value come strictly from the fact that “it is an unopened box” or is it because of the value of the cards inside. (because everyone is like “OMG this is where you can get the XXXX 25,000$ card in it!!!”)
But if there are a lot of box openings it will increase the amount of PSA 8´s to 10´s which would (in theory?) decrease their value. But if the box prices were strongly correlated with the card values inside there would be no reason for the box to surge in price that much in the first place. The reason for that would be imo the pure fact that it is a sealed box.
Does anyone have an opinion on about what are the main factors for the extreme prices of boxes in relation to the graded cards? Don´t get me wrong I´ve seen the singles gain a lot of value as well but I think not as much as sealed boxes.
I hope I could clarify what I mean with my question, if not I can try to explain it in an answer below.

(Greetings from Germany)

@marci, Your post is in the wrong section! Feel free to repost in the Giant Market Thread.

www.elitefourum.com/t/the-giant-english-market-thread/27424/1