Only ones I was involve with, back when supplying in the trades, were more than that and percentage difference significantly more than traditional framing and brick exterior. I bet it does start to look more attractive comparatively with what the price of wood is these days. Metal studs may also be more attractive. I was supplying high-end hurricane rated windows and being real picky on their mounting, as compared to standard Tennessee construction techniques.
IDK. The hitch has always been getting the ICF forms. A friend of mine replaced the house on his wife's family farm with a smallish two story poured concrete house and it took him about three years just to be able to get dried in. He had a real time getting all the forms he needed.