As you can see, the price for the white B-ES balls is an anomaly, not the rule. It's the one price that stands out among all the other prices. The price range among all the other types of balls & colours seems negligible, whereas there's a whopping discount if you buy the no-frills white B-ES balls. I for one am thankful for the huge discount.
Still, B-ES is my least favourite type of upgraded balls because, once you get used to the extra distance provided by B-XD & GI-D, it can be pretty difficult to readjust your mental calculations back to the regular distance of B-ES balls.