Plato is pertinent to this because the individuals that wrote the founding documents of our actual government were influenced by his writing. The Plutocracy was your point, not reality. I do not think you even made a good argument for it in the first place. Since I do not think you are saying that wealthy people actually have more power and resolve than the federal government itself then you must be talking more about policy. Money is only an advantage in swaying policy because so many people do not vote and or pay little enough attention that sound bites and advertisements can buy their vote. The most broken part of our system is in the apathetic and unintelligent majority, but that is not the same thing as having an institutional barrier. In a lot of ways our current system really hasn't even been tested, and really won't be until all citizens exercise their power to vote.