I think the cost discussion is a kind of trap that Montezuma and Bernie have sprung. Their only chance to stop the I4 turbos is to make them more expensive than they would naturally be. By themselves I4turbos would be a lot less expensive to manufacture as long as you apply reasonable resource or budget restrictions to the development. The problem is that Ferrari have no interest to agree on restrictions that would enable Cosworth to develop a competitive engine. That way they can blackmail the FiA into a change of plan.
Unfortunately the small turbo plan massively hinges on Cosworth to be able to supply three, four or five teams with reasonably competitive engines. So there is the obvious opportunity for Ferrari to screw the engine plan. Cosworth according to Autosport article are still dedicated to the 2013 plan but they fear that Ferrari will trigger a cost race unless budget or resource restriction apply for the engines similarly as they apply to the chassis development.
It is now quite open how this will pan out, but I have a lot of faith in J. Todt to sort this out. After all it just needs a majority vote by the teams to apply some sensible form of cost control for the new engines. They are likely to sign up for something like this in order to get cheaper and greener engines.