just a random thought here, tossing history pages at like 0.1% & BMP at like 0.5% chance from L4 boxes, pg1/2 from basement, 3/4 from 1f, 5/6 from 2f and 7/8 from 3f. Would still be massive grind, at 0.1% you're looking at avg 4,000 boxes to get both the pages unsealed from each floor, but it'd be an alternative path to farming L4 bosses. Naturally BMP & Pgs 3-6 would be devalued as 1f/2f are grinding floors anyway, would give more reason to grind basement & 3f, and increase pg 1, 2, 7 & 8 value.

interesting thought, I like it but, I'm gonna assume the 4f farmers wouldn't so :P