Location, location, location!
Do you understand the concept of “the gravity well”?
(if not, watch this: http://www.youtube.com/watch?v=VBQHtF3WhMw)
If so, you know that it is very expensive in energy & hardware to lift equipment or materials up out of that gravity well to Earth orbit & beyond.
Materials on the Moon and equipment made from them are at the bottom of the Moon’s gravity well, which is 1/22nd as large as that of the Earth. Thus, lower energy cost to get them to space.
We do not need pig iron on the moon, especially at a cost of $1 billion/oz.