Those royalties were at rates controlled by the government and as I understand it were fairly limited. No doubt there were significant shortcomings in the USSR though, this among them. Sort of in line with the general problem of different wage rates. I believe the highest paid workers had wages about 5 times those of the lowest paid. As the Soviet Union decayed more liberalism entered its copyright system, the rate controls were lifted by Gorbachev and even before that copyright was made more restrictive with respect to translations and foreign work.