Aaah - this old chestnut. Just a skim through
www.avherald.com and you could easily see the lives that could potentially be lost should the flight deck complement be reduced from what it is today. As for those who dream about pilotless flight decks - dream on! Just in the last few years, thousands of lives would have been lost without human intervention from those 'on the spot'.
Yes - the industry DOES factor in cost of safety/improvements etc versus cost of lives. That has certainly been the case for many years.
And yes - there is a good amount of human error. But at the end of the day, these same humans save more lives that they cost. I could never say the same for today's aircraft computers.