"The rich guy can buy a harvard education, and the poor guy can buy a cheap but effective online education"
And what is the outcome of having Harvard education against having cheap online degree? I am sure Harvard graduates come way ahead of graduates of online universities, both in private job market as well as in influential government positions due to "cliques" and "networking".
But the problem is much deeper than whether you can afford high quality commodities or not. Those with excess capital can accumulate assets, and then rent out those assets to those without capital. If this sounds too abstract, consider a concrete example - bay area housing market. Only those with capital can afford houses. Those with excess capital can buy additional houses and rent them out to those who cannot afford housing. Net result? The ones who cannot afford houses now have to keep paying rent to those who could, thus making homeowners richer.
Piketty has elaborated this in detail. But the most salient question he raised was that inequality, per se, is neither bad or good, but whether it is justified? Today, Bill Gates or Mark Zuckerberg have billions more than I do. But I am OK with that because they took risks, invested their efforts (and yes, also got lucky). But I am don't think someone like Alice Walton or Paris Hilton deserve their billions - in their case, all they did was just to be born to rich parents. And they and their heirs are going to have a better life (education, nutrition, accommodation, entertainment, connections...) than almost everyone else. Why? Doesn't seem "justified" to me.
Edit: Why the downvote? And while I respect your freedom of speech (to downvote), I am sincerely interested in knowing your counterarguments.