After 600+ VPs and especially after 1000+ VPs RBs can only be taken down with fully boosted (8-10 boosted attacking statues) maxed out troops and great attack skills. Eventually the RBs will max out (there is no more space to add new defense and all defenses are maxed out). People who try to throw diamonds there are the ones who did not master the attacks. Granted, a person with unlimited diamonds can instant finish the troops and keep attacking while the boost is burning. However, a great attacker will take it back in just one attempt. So, eventually it all gets to the point of who is better in the game and not who has a fatter wallet.