This is not “certainly not”, because what you’re saying is true, but it doesn’t contradict my point. What I mean is that putting the gold and the decorations aside, the quality of material is what makes the armour cheap or expensive (by the way, this is true even nowadays). I think you agree that the combination of cheap bad armour with expensive decoration is possible, but unlikely to be anything other than a decoration itself or a ceremonial item. On the other hand, if you can afford putting an expensive decoration on your armour and you are going to battle in it, you can afford making it good, otherwise it would be silly. But removing the gold from such an item, while will make it cheaper, won’t necessarily make it affordable or, more so, mass among ordinary soldiers. Moreover, if you need a good piece of armour, but you can afford either good material or expensive decorations, but not both, I think you’d prefer the first option.