Wikitravel Press presently distributes its books through CreateSpace, a division of Amazon.com. Book prices are agreed mutually between editor and publisher, with a target margin of $5 between production cost and sales price, as computed on this page.
Wikitravel Press uses the Pro Plan, which has a one-time setup fee of $39, and we are required by CreateSpace to print and ship a proof copy for each revision, which costs ~$10 in the US. These costs are shared by the author and WTP according to the agreed royalty percentage; basically, for the first 10 books or so, neither editor nor WTP make profit.
Getting good reviews of your book on Amazon is absolutely critical. Give or lend your book to friends, relatives, colleagues, Wikitravel buddies etc and ask them to write a review for you. While adding reviews to Amazon is very easy, many people (especially the non-computer literate) find the idea intimidating, so follow up and be ready to help out. However, do not fake or ghost-write reviews; this is severely frowned upon by both Amazon and WTP, and may see your account or book pulled.
Wikitravel Press will submit your book to Google Book Search, which provides a steady stream of interested traffic to Amazon.