How much money would his notebooks be worth

I'm not talking about selling the notebooks to villains or hero's but, yknow how in some fics izu gets hero's autographs on their page on his notebook.

well if he flat put does that with every hero he meets [this is just assuming everyone of these hero's are on 1 notebook]

how much money would his note book be worth for every single autograph.

like- he does meets loads of hero's he could get a autograph from, even from hero's who autographs probably aren't publicly known like aizawa