Steps for reproduction:
1. Launch a 1v1v1 private game.
2. Have 1 player surrender.
3. Have 1 player kill the surrendered player's command center.
4. Notice $400 is given to the player that kills the surrendered player's command center.
Notes: Not exactly sure if you would consider this an issue or not. On one side, the player is no longer fighting back and it is jsut free money at that point. On the other side, players could surrender right before the death of their command center and in a large free for all match, it would not give anything to the player that spend all their time trying to take out that one player.