As I said waaayy back at the beginning of this thread: The odds are very much in favour of the FDR and CVR being recovered, not the other way around. Those who write that finding them will constitute "a miracle" are not up to date on current technology and methodology.
Yes, this will likely turn out to be an incredibly expensive investigation, but it will be done. Despite those on pprune who speak of conspiracies amongst the investigative agencies, and/or the manufacturer(s), the truth is that the incentives and rewards of a thorough investigation make it far more worthwhile to those agencies than any alternative.
grizz