There is a reason for that. To get a bit (light) is easy, to get average (medium) only slightly harder, to get good stuff (heavy) it starts getting expensive, but to get the very best, to get the very best of everything (plate) is extremely costly. Otherwise everyone would just go with the very top end.
With weapons it is different, since you have damage, reach, speed, etc to consider, however with armor its protection vs weight and cost, so I agree with this being so. You want that extra point, that special look? Pay for it.