For the conspirators who murdered Caesar the price of ambition is very high indeed: death. But it wasn't supposed to be like this. Caesar's murderers believed that once the Roman dictator had been murdered, his former friends and allies such as Mark Antony would fall into line. They also believed that the plebs, the common people of Rome who adored Caesar, would accept the new order of things.
That certainly seems to be the case after Brutus gives his funeral speech to the Roman people. But before long, after Mark Antony cleverly turns the plebs against the conspirators with a rousing speech of his own, the assassins' hopes of a smooth transition of power lie in ruins.
In the ensuing civil war, all of the conspirators pay for their ambition with their lives. Some, like Brutus, Cassius, and "envious" Casca, commit suicide when it's clear that they're on the losing side. Others, like Metellus Cimber, die in battle. Even if all the conspirators had been captured alive by enemy forces, it's certain that they would've been put to death, as, in the play, Octavian, Mark Antony, and Lepidus draw up a lengthy list of traitors who are to be executed once the triumvirate has come to power.