They don't pay much more at all. The argument doesn't hold water.
Big allocations are cheaper per IP than small allocations.
Our little planet revolves around money. I agree with the essence of what you're saying here. I think this will be important in getting buy-in from the general population that will be looking to get IPs. ARIN may be looking at nasty political or legal ramifications if they don't. And in many ways, they will be right.