Wow...lots of questions...but only a few regarding the title of the thread. The title..."How important is Crashworthiness?" has naught to do with payload, fuel burn, etc....unless I suppose one has to reduce pax seating/payload capacity to accomodate "crashworthiness measures". Within the framework of your question do you consider losing two passenger seats and a 25% cost knock out of the starting gate a cost?
How does the customer calibrate his cost analysis parameters when weighing "crashworthiness issues"? Does a customer who is quite happy for his employees to be flying over rough cold water just prior to dark in a single engine aircraft with no SAR coverage even consider such issues? If they do....why would they not opt for the most "sophisticated crashworthy" aircraft money can buy. Sheer cost would not be the issue but rather buying the cutting edge tech aircraft would be.
If we wish to fly around in "proven" aircraft we would still be in DC-3's instead of RJ's and 737 XXX models. Have not the new high tech "crashworthy" aircraft shown themselves to be superior to the old tech....less "crashworthy" aircraft over time?
A thought to consider....statistically...the Bell Jetranger is the safest general aviation aircraft in the world. Despite being operated in some very dangerous work. How does this play into your question....for sure the Jetranger is neither hi-tech nor "crashworthy" as it is applied in this discussion?