You can do just one solo Dynamis currency farming session, and have enough Void Clusters for two weeks. Three or more if you are skilled at soloing that/lucky enough that the zone is empty. Then there are many other methods of making easy gil nowadays. I can understand saving Clusters if wanting to help your LS in advancing through VW tiers much easier, but at this point in the game, those claiming to be too poor to buy them are just being cheapskates.