How much does it cost to set up a wiki?
Setting up a wiki is a quick and easy process that costs very little in time or money.
Wikidot wikis can be set up in just a couple of minutes, and Wikidot will host five 300MB wikis for free. (After four and a half years of constantly adding content the entire LGAM Knowledge is still only about 240MB in size.)
MediaWiki is a totally free open source product, and it should only take a couple of hours to set up. The only other consideration is having space on your servers on which to host it.