This is probably cheaper than the other links, but not by a whole lot.
I'll start with a list of materials:
1. Cherry MX reds -
http://www.wasdkeyboards.com/index.php/ ... inear.html - $7 w/ shipping (don't forget to buy keycaps)
2. 16 Gauge steel hurricane tie from home depot(you can get this which is zinc coated, or just the full sheet which is $10. The Tie has SIMPSON Strong-Tie NS2 16Ga. on the front) - $0.40
3. Keyboard or keypad from Good Will(you have the option of usb or ps/2 here, doesn't matter too much) - $2-6
4. Some sort of base, mine happens to be aluminum. - $?
5. I use protoboard on the switches, if you want to go cheap, you dont have to use it. - $3 (if ordered from china)
6. Solder / wires / nuts / bolts, I used M4 bolts and 60/40 lead solder - $10 (I could have probably got this cheaper)
6. Maybe some sand paper for the base and glue, to keep it from sliding - $1.50
Total Cost - $15 - $25
Tools: I used:
1. Hand drill, for the silicon boards, and 3/16 drill bits
2. Drill Press for the metal, not required but nice to have
3. Jig Saw with a metal cutting blade
4. 3/8 drill bit to get a starter hole for cutting out the switch holes
5. dremel with a cutting / shaving blade, you can proby replace this with a hand file, as long as its less than a half in wide
6. 40 watt soldering station
So, basically you can get the specs on the switches at
http://cherrycorp.com/product/mx-series/It's pretty hard to get the switch holes, exactly to the measurements, so I started at a half inch, and shave to fit with the jig saw, once I was close I polished it off with the dremel / hand file.
A lot of your projects size / dimensions are going to depend on the controller you manage to get your hands on. Once you find a random keyboard, you will need to tear it apart pull out all the rubber stuff and the plastic sheets, and just take the controller and the cable it's attached to.
In order to find the Z and X keys, you can either trace the circuit on the plastic sheets, or just try shorting 2 pins together until it starts printing stuff on your screen. You definitely don't have to grab Z and X, as you can just remap it in game.
As far as the rest goes, the hardest part of this project is having the correct tools to cut metal. If you don't have any, then this will end up costing you more than the links posted above. You could think of them as an investment, however :p
I was considering building and selling them, but I would have to sell them for $30, which isn't exactly cheap, and why buy mine when you can buy one that actually looks good.
Thats about all the time I have atm, if you have questions let me know!