Heat is exponential, a 50% clock reduction will remove the heating issues and greatly reduce demand to ~40w, totally viable on a mobile platform.
400$ chip, 400$ card... even with the laptop tax it shouldn't be over 3k unless you're putting too much weight on making your box a fashion statement.
I don't really follow the industry anymore since getting a cushier job, I just want a travel laptop that has some actual grunt behind it without popping breakers or weighing 25lbs. From what I can gather, those chips are simple, small, overpowered, and easy to mass produce. Won't be long before we see them everywhere. Makes sense to me to see them go all in with that 3d cache tech.