I'm no metalergist, but I suspect the cost of a solid brass hammer may have been more (one-off type things), and I don't know if brass plating would work. These people weren't stupid, and there were a lot of people overlooking all the engineering aspects (in-house and Gov't). Though there were multiple programs in progress (tiles for the shuttle, and some of super-black programs), there were 28,000 employed at Lockheed Sunnyvale at the time.

SGE