I've spent about 15 today for wood and screws and built mining rigs out of wood, each able to hold 5 cards. Took me 30 minutes to build both.
I don't think you can get much cheaper than getting some wood and screws and building it yourself.
What the motherboard sitting on? Care to post a picture or 2?
Also, anyone using anti-static mats under the motherboard (for the metal and wood framed cases), not that you need one?
Thanks