I think the idea is that extraordinary claims require extraordinary evidence is the main factor is the "less funded" charities. Appeals to emotion are seen as either manipulative or not extraordinary enough. Appeals to intellect (a million is a statistic?) are looked upon as more favorable because you can tell what actually happens.

Many people might disagree with you but I think you have the right idea here. Some people might just disagree with selectivity in the way you interact with others. Does LessWrongers believe that selective interaction is morally or ethically unjust?