So where do you put the cables? The stands look sharp but after adding cables it seems it kills the look.
these stands look like there isn't a top platter and that the stem is connected to the thermal core. (as in- i doubt those computers are just sitting/balancing up there)
so you have to imagine if you have one fabricated, there will also be more showing (a top plate).. i assume you'd want that plate to be a bit bigger than the circumference of the mac pro which to me, makes it look even worse.. and would probably require a larger bottom plate for stability in case you don't have the mp dead center up top.. (unless you want to use a noprofile plate which bolts to the base of the computer)
and your (phrehdd) mention of the cables also brings up a good point about aesthetics as they'll be dangling down (gonna look like a long haired mannequin head)..
anyway- if you want to spend money on a custom fab job like this, don't copy this design.. this design is for non-operational models inside a glass case and it serves a purpose (for instance, the 2nd from left version couldn't just sit on the table).. so customize it for the location it will be used in-- a working computer on a desk (or where_ever)
point being- i think you could come up with something a lot better than these if you want a mac pro stand for real world use.
[edit] hmm.. i'm sure a few people shot some photos at the event which inadvertently show the connection point via the reflection in the bottom plate.. i'm not going to start searching for the pic though