How much power is enough power?

I'm not saying buy low and sell high within itself is corrupt. I am saying that overindulgence of it is. When someone makes it their life's work to underbuy/oversell rather than actually playing the game (training/bossing), they've been corrupted because of it, and because they are obviously greedy. Wow, some of you guys catch on quick.

Like I said above, when you're overdoing it I think it's greedy and corrupt.

See above.

At what point is it corrupt? Maybe greedy, but merchanting is an acceptable practice by nearly everyone in the free market, and there is nothing wrong with it, nor has nexon held any guards against it. There is nothing "corrupt" about it.
The only point I draw the line is when one person buys out all stocks of specific, high in demand items to resell at completely ridiculous prices because said person has full monopoly.