Purchase one copy for yourself and one copy for a friend. This of course for the US and Western European consumers.
Of course, about 99% of the "consumers" in Russia and Eastern Europe will just get pirate copies and pay nothing. This is simple fact. There is really no legitimate Eastern European software market. One the one hand, there is no law but Mafia law--it is absolutely impossible to enforce Western intellectual property law in Eastern Europe. Just forget about it--not even worth the trouble. Even to get the Eastern European judicial or law enforcement systems to combat piracy would take so much bribery money as to completely offset any potential gain. And furthermore, even if piracy were completely stamped out, the poor citizens of Russia and Eastern Europe are suffering such terrible economic devastation that the idea of purchasing software for a real price would be totally ludicrous. There is not even enough money for simple food and clothing for the children, much less for games. Excluded from this misery of course are the non-Russsian Mafia brats of Moscow and St. Petersburg. Perhaps they can afford to pay, and if there is an "Eastern software market" perhaps that is where it is.
Simple marketing rule on software is that the money is made in the US market. That is why the US market is always first served and why the interests, tastes, and desires of US software consumers are given the greatest level of respect and attention by software people. Europeans complain that the typical US software consumer is less intelligent, more primitive (in a caveman kind of way--think: football and console games), less refined, less able to appreciate creativity and good work in software games. But the accountant's bottom line is still that this same US consumer is the one who is going to pay all of the bills. Whether a game succeeds or fails is almost completely dependent upon how this "brutish" US consumer responds to the pretty box. Oh, and add South Korea to that as well. They must eat games there, because they buy so many. Maybe sad, maybe bad, but that's the way it is!
Again, though, CK will be a good game (because EU and EU2 were so good), and if you can afford to do so, you should buy it twice to support the game designers for their good work.