A wiki is a good idea in practice, but you're right that they take up phenominal amounts of time in their setup as well as to author pages, and keep feeding updated content. I fully appreciate the problems, and admit that many a good idea can quickly fall by the wayside due to lack of time.

Starting small may be the key. We have a wiki of sorts don't we? (Main Page - PrePaidPedia) I suppose one way of getting started is to makeup a generic template of a table. Someone who wants to take 'ownership' of a country could then quickly create the country page for his/her country in the wiki, and cut and paste the template table into the wiki page and fill in the contents of the table. Ideally he/she should maintain it from time to time too.

I'm sort of thinking of a table like this: (The example here is Spain)
http://img.xatakamovil.com/2009/08/complowcost.PNG
Of course I would also propose to add a few extra columns like cost of SIM, call setup cost, international voice call to a chosen destination, international SMS etc.

Anyhow, just ideas for now. Obviously I fully appreciate if this may not happen for a while...

no one mentioned the effect of VOIP solutions... on my last trip I used Skype more than my int'l SIMs... a LOT cheaper... and can be used on various handsets like WM smartphones...