Not sure if these would be unexpectedly high values as most people know they fetch a little bit, but I have all my old N64 games still boxed with most of the original inserts too. The one I know most would be Conkers Bad Fur Day, that always seems to fetch a nice price.
A couple of my Funko Pop figures are possibly worth a few hundred but nothing more.
And I have the full set of Hobbit and Lord of the Rings Lego sets which I know go for a bit over the original price.
From what I remember reading, yes there is some added content from the books that is not in the musical stage adaptation. I think it’s more of Elphaba’s childhood (which is quite a bit in the book).
Also remember reading that one of the reasons they decided to split it was because they couldn’t find a reasonable way to move on after “Defying Gravity” (This is the big number before intermission in the musical and really does feel like the end of that chapter) to the next scene in the film, so they decided to split the films too. Not saying it was the best way to go but maybe it means they can add more book related stuff to the second half too. The musical is sorely lacking there too.