I agree that only comparisons *within* countries in WWII are really meaningful. It would still be interesting to see comparisons like US v UK though, or any solid data outside the US.
On profits, maybe it gets too political, but the assumption that profits are an addition to the cost of something you can just make go away by govt control seems to have been fairly definitively proven wrong in the course of the 20th century. The profit motive creates efficiency, that's the missing piece. Assuming there's some competitive pressure of course. And pure patriotism is worth something in a wartime situation. For example the Soviet economic system proved ultimately unworkable, but patriotism (and fear) partly compensated that, especially in the crisis of WWII.
On the US planes, the costs came down a lot per those USAAF figures, and that's typical of US weapons (small arms, tanks similarly), so it doesn't seem the companies were actually in a position to set any price they liked regardless of their costs; as costs came down with volume and learning curve, so did prices.
Joe