What was Big Willy Shakes going for?
You'd think it was enough to be the nation's greatest warrior and Thane of Cawdor. What more could a man want? Apparently, a lot. Once Macbeth has had a taste of power, he's willing to kill anyone (and we mean anyone: men, women, and children) who he thinks might undermine his seat on Scotland's throne.
But Macbeth doesn't get to enjoy being a gangster for long.
He puts his own desires before the good of his country, and, in the end, is destroyed by that ambition. So, maybe you should lay off that nefarious plot you're cooking up to become class president: according to Macbeth, the power and glory just isn't worth it.
Put simply, Macbeth is wondering how much is too much. How much will he have to sacrifice or give in order to get what he wants? Will the cost be too great? Will the crown be worth it?
Ironically, it turns out that the murder Macbeth is contemplating (of Duncan) is not the be all and end all for him. In fact, it's far from it. He goes on to murder loads more people in order to keep the crown on his head. It's only a matter of time before all that murder and mayhem catches up with him.