I think you have hugely overestimated the rate at which you could produce completed devices, and hugely underestimated labour costs for labour-intensive production processes. 80 per hour is 45 seconds to assemble a completed unit, and that's barely enough time for even one or two cycles of quill spin-down, toolchange, and spin-up, let alone enough time to mill a complete part (or assemble that part into a final assembly).
For comparison, here is a semi-automated case production house (Lian Li), a a semiautomated PSUI production line, and a fully automated PSU production demo line (Silverstone), and a mostly automated case production line (In-Win).
The universal use of stamping and turret-punches is because they are dramatically faster than any other machining process, and time is money. Even Lian Li, who specialise in boutique cases with short production runs, limit themselves to performing as few operations as possible with laser/plasma/water cutters and doing as much as possible though stamping.
Also on that note I am not suggesting it is cheaper. Just that the cost of doing so compared to the costs they are being sold at I am struggling to understand why we are not looking at much better quality products relation to the cost. OK of course it is profit etc but my concern is that the budget £40 units are finished better than a lot of the SilverStone products which often look like they are prototype products being sold as premium.