And considering they use four identical boosters for each, that's 60 to 80 cores per year. More than one per week. If they move to RD-193 engines that are used by the Americans as well, even more economies of scale.

Encyclopedia Astronautica posits that the Soyuz design is a multicore version of the German-designed Gröttrup G4. http://www.astronautix.com/lvs/g4.htm