Alright then, use wood. Picks up less static than the cardboard and is still relatively cheap. I don't know why you should waste $60 USD on a metal prism.
Because it looks like stuff
Next question.
EDIT: Also, most "metal prisms" have cable management, already have the standoffs in place, places for fans, a secure place for both front and back IO, secure places for all drives, PSU, and other. Sure, you can make a wood case, but it would take a stuff ton of time and might not even look good if you dont take the time to sand it and stain it.
I can see a wood case being amazing, but youll spend a bit of money and time and takes skill to do.