Only quoting here from Deighton's "Bomber" but of course may very well be incorrect:
In cash, at 1943 prices with profits pared to a minimum, each Lancaster cost £42,000. Crew-training averaged out at £10,000 each, at that time more than enough to send the entire crew to Oxford or Cambridge for three years. Add another £13,000 for bombs, fuel, servicing and ground-crew training at bargain prices and each bomber was a public investment of £120,000.
As a side note I was once taught by an elderly schoolmaster whose job he said during the war was to go around with a dustpan and brush and "sweep out" the bombers.... it was only many years later I understood fully what his meaning was, it was the way he said it and how his eyes glazed over that made it stick in my mind.