The 1UP kits are quite far from cheap unfortunately.
If you want the absolute cheapest kit possible and are willing to buy from Taobao etc, you can do something similar to this:
http://www.haroldiv.com/?p=15If you want something slightly more expensive but much better quality, check out the 60% PCB kits/parts from te KBDFans, KPRepublic, and YMD Keyboard stores on their websites and ebay/Taobao/Aliexpress.
