I understand your point about the business end and the cost of using ARC FAULT CB's, however, didn't they (tradespeople) say the same exact thing about using GFCI's when they first came on the scene?
I haven't read everything on this thread, but it is interesting to know that there isn't even an ARC FAULT tester on the scene yet they are required by the NEC. That does not make sense.
Your point about using them on old-wiring compared to using them on new wiring is also a good one.
