I'd say that milling it out of a solid piece of metal would be too cost-prohibitive. 2"X13"X5" or whatever pieces of metal aren't cheap, and there's a lot of waste.
The way I see what he means is that they'll cut out a "plus" shape, then fold the corners up, and weld the edge. I imagine it'd look excellent.
Now does this go around (cover) the plastic case, or replace it entirely. If it's #2, I'd be interested in one (for a Cmstorm QF rapid).