Without seeing the book, without knowing the page quality, and without knowing the pedigree (some pedigrees sell for less), and without even knowing if the book is slabbed you are going to predict a selling price. You're good !
I simply assume since he seems confident in the way he says 9.0 that it is slabbed, and yeah I know my stuff .
As far as page quality goes, I mean let's be honest that means very little in the grand scheme of things. Any book that is different in page quality and nicer than it's counterpart might sell for a hundred or so more, maybe a few hundred but even that would need to be a big book like a high grade DD1. I feel like we would need to be talking Action Comics #1 or something at that level for a nicer page designation to really make a difference in thousands of dollars. As far as your mention goes about not knowing the pedigree, I honestly have no clue. I don't know what specific pedigree might sell for less or more than another, but I do know that on the average a pedigree copy will outsell a regular copy of this or most any comic. So with Daredevil 1 CGC 9.0 in the $7,500-$8,000 range I imagine a pedigree copy whether with Off-White to White or White pages will sell for around $9K, give or take $500-$1,000. Anyway, there's my logic for ya. I feel like it's pretty sound .