Acknowledged, but you are comparing only to famous and expensive cities.
So to make the ranking more fair - e.g. I've been living in Kraków which is more than 40% cheaper than Berlin in every aspect (though I'm not recommending it for a rationality hub) http://www.numbeo.com/cost-of-living/compare_cities.jsp?country1=Germany&country2=Poland&city1=Berlin&city2=Krakow+%28Cracow%29
And I'll be going on a 3-month vacation on Malta, which is also visibly cheaper: http://www.numbeo.com/cost-of-living/compare_cities.jsp?country1=Germany&country2=Malta&city1=Berlin&city2=Birkirkara
A lot of the people on LW are programmers and thus want to be employeed by software companies. Those generally exist in big cities. Big cities also tend to draw a lot of diverse ideas.
I can talk to someone in Berkely about Circling/Authentic Relating because there are Circling Events in Berlin and there are Circling/Authentic events in Berkely.
I haven't checked but I wouldn't expect to find Circling in Kraków or Malta.
Malta happens to have some interesting properties but I would guess that it would take significant financial resources to build something there.
In short, I'm wondering what place/group/organisation/activity could do for rationality in Europe what Berkeley does for rationality in the US?
Soon, we'll have LWCW in Berlin, which I hope will be an occasion to do some networking among people who think seriously about developing rationality communities. But in the meantime, let's do some brainstorming.
Important note: in comments to this post, please use only consequentialist language. For example, say "If we decided for the base to be on Malta, then X would happen" instead of "I think it should be in Malta, because..."
Of course, share anything else that you think is relevant to the topic.
Also, see you all in Berlin :)