As far as why white might possibly cost more, it's easier to get something dirty than it is to get it clean.
It's possible that the process to dye the silicone a bright white is more costly than to dye it black or a color, therefore, LELO passed on the expense to the customer.
I wanted the white wand when I purchased this toy, but my wife wanted the black one. See my review to see who won, although you could easily guess. ??