It really doesn't matter if they are or not. In order for communism to truly work, you'd need to abolish all rewards. That is, the very act of having hockey players and cosmonauts and musical talent recognized by the state at large - regardless of financial reward - creates the very imbalance that communism is supposed to address. As I said: self defeating.

People may seek different rewards based on their character, but the very nature of man is that we work best when challenged and respond will to the rewards earned when overcoming those challenges, financial or not.

If your economic system essentially requires a man with a gun to ensure and enforce its existence, there is something wrong.