According to D. S. Hutchinson, in the article "Ethics" in the Cambridge Companion to Aristotle, a democracy "claims that all freely born citizens are equal partners in society, and oligarchs claim that the rich contribute more." The principle is that, justice demands that what an individual person puts into an enterprise will be rendered to them in the appropriate ratio. If two partners each put in 50%, then they each receive 50% of the profit. The democratic argument is that all citizens contribute equally to society, and, therefore, all citizens should receive equal benefits from society. The normal position of an Oligarchy is that the rich citizens put more into society, and, therefore should receive more benefits. It seems to me that neither side is right. It is not true that all citizens contribute equally to society, therefore it is unjust for society to give equal benefits to all citizens. On the otherhand it is not necessarily true that the rich people in society contribute more to society, if we look at a monetary investement then it might be argued that they do. However, it seems that one can also invest their time and their life in society, and these seem to be worth more than all the money in the world. Therefore, it seems that those who invest the most in society are those who give their time and lives to helping others. If this is the case, then a true Oligarchy would be led, not by the rich, necessarily, but by those virtuous people who give their time and lives to helping others. This is very much the same conclusion that Aristotle comes to, according to Hutchinson, who says, "Aristotle himself holds that virtuous citizens (not necessarily the rich) do make greater contributions to their societies, and that they should expect greater rewards in honour and respect."
If such an Oligarchy existed, its society would be...well...pretty close to heaven.