Seeing how geekhack is down and my googlin let me down too; the Phantom plate for instance, how/where was that done?
I'm interested since I'm looking to have one cut for me, don't see my dremeling do it precisely enough; and the one source I thought was gonna do it for me for free ended up not being able to cut alu/steel at all.
Why I'm even looking at cutting a plate, is, 7bit selling plate mounted switches, and me wanting a matrix/staggered collumn layout. So reusing boards is either costly and dumb, or not possible.
So as far as I know, the plate needs to be 1.5mm thick, at least at all the spots the switches click into place, and thus for rigidity either aluminium or steel; and even then probably needs multiple posts underneath it to reduce bounce.
Gimme all those succes/horror stories!

For me, I jumped on the switch MO to get a feel for all mx's on the cheap so I could order a proper keyboard afterwards. Already have spent 200 on keys/parts/boards so far, and still have the case and plate to go. So that works out.

*edit: changed title to reflect the main aim, minimization of costs.