On thee other hand, the NEC code changing panel is made up from SEVERAL individuals desputing over very concernable debates. The NEC is not in any means profitting from their decisions. These are decisions made with the customers safety at hand. I don't think they or any supporter of the design are trying to SCARE anyone or make anymore money.
Yes, of course cost is of concern, but if arc faults lie in the small percentage of possibilties, than the cost is over run by their integrity and piece of mind. Even though it is code, I have worked for a couple of contractors that have said it was not of their concern, (in remodels), and that if circuits were constructed properly, than no further safety concern should follow.
Of course, this is one of the scenarios where I walk away and tell them to have someone else do the job. I either work my way, or the meeting is over.
I do NOT see this as TR or ground up/ground down issue, not even in the same debate. Let's do it right for the customer from the get go.