There are about 100 to 120 grade 'A' beans (6-7 inch) per pound (7.5 per oz). 30% – 35% moisture content.
Grade 'B' vanilla beans (also called extract beans): about 140 to 160 grade 'B' beans (6-7 inch) per pound (10 per oz). 15% – 25% moisture content.
Related:more vanilla information