Basically, 9.0-9.5 mm Japanese Akoya pearls are considered extra large for its kind; meaning that they are extra rare and expensive accordingly. Though, when worn by a tall guy, they don’t look that large. I think that this is an opportunity for pearl marketers to sell the goods in premium size to male customers. In general, fashion and beauty products which are specially made for men are extra expensive anyway, because they are somehow considered tailored-made for specific needs.
