I looked into it briefly, when MD was doing a run of just the PCB (hadn't found MechanicalKeyboards yet ... they have them, and four dollars cheaper to boot). A coworker's father works in a shop with CNC machines but said they charge $75/hr to set the machines up, plus materials and something nominal for making the machine cut into metal.
Also, and I hope you might be able to help me, all I found were the files that were sent to Shapeways ... 3D printing, which could sorta be converted for CNC'ing a two-piece case but surely it'd be simpler to cut from five sheets of metal like the acrylic case is but I absolutely COULD NOT find evidence of a machine-readable description for that version of the case.
Any help on looking stateside for getting cases made? As in, files I can carry around to say "cut this" ?