This isn't true actually. Aerospace grade aluminum, for example, is much more expensive and since you want to minimize weight with ortho- and iso-grids, you're

This isn't true actually. Aerospace grade aluminum, for example, is much more expensive and since you want to minimize weight with ortho- and iso-grids, you're throwing at least 50% of the material away. Another problem is that you not only need to consider the "base metal" of the part you're cutting, but also the cost of the tools that do the cutting (ignore the machine itself). You're consuming a lot of expensive endmills to get rid of the material.