One interesting question about salvation is how, exactly, does 3 hours on a cross equate to an eternity in Hell? One might argue this is the equivalent of settling billions of dollars worth of debt by tossing a penny in a fountain. But doing so requires us to set aside one critical element of Christianity: The Deity of Christ.
As finite beings, we receive (or at least, we are owed) eternal wrath for our sins, since the God against whom we have sinned is, Himself, eternal. Christ, however, when He took on mortal flesh, did not likewise take on a mortal spirit. He was, and is now in His risen body, God in flesh. Therefore, the eternal element is not removed, but shifted. Jesus, as an eternal being, did suffer an eternal punishment.
This is one of many reasons it is vital to understand the doctrine of the Trinity. If we see Jesus as purely man, but in no way God, we see Him with our limits. Even in His power, we see Him as no greater than Moses and the prophets. If, by contrast, we see Him as purely divine with only the appearance of a man, as Gnostics, we separate Him from ourselves, removing our substitute. Only a proper understanding of the Deity of Christ can fully account for difficult questions such as this.