The only way the story of Adam and Eve makes sense is to understand that God not only knew how things were going to end up in Eden, but that He deliberately set the whole thing up to make a point. What point? This one. If Adam in paradise, without a problem in the world, could not manage to obey one simple command from God, what chance does any human being have of living their entire trouble-plagued life without sinning either in word, thought or deed? No chance at all. That is the lesson that was illustrated in Eden. Human beings have a sinful nature. A nature which God gave us.
Why did God give us a "sinful" nature? Because "God is love" He wanted to create people whom He could have a loving relationship with. But since true love can be neither forced nor programmed, in order to have loving relationships with us, God had to create us as free people. Free to choose to love God and His ways or to not love God and His ways. In other words, free to do both right and wong, free to do both good and evil.
Because we can do wrong and often do, and because God can't do wrong and never does, we are less righteous than God. And because we are none of us deserve to live forever. That means all human beings have, in effect, from their births been condemned by God to die. Not because of anything Adam did, but because we ourselves all fall short of the glory of God. (Romans 3:23)
So, the Ransom really had nothing to do with Adam. The sins God holds against us are our own, not Adam's. And our sins are what Christ gave His life to pay for.
Why did Christ have to die to pay for our sins? God's standards are very high. He long ago decreed that only those who are perfectly righteous are worthy of eternal life. Of course, this meant that God had in effect also decreed that all who are not perfectly righteous must die. But despite God's extremely high standards, like many loving parents, God has always wanted to give His children more than they deserve.
So, God was confronted with a dilemma. On one hand, He had already decreed that only those who are perfectly righteous are deserving of eternal life. Thus He had, in effect, demanded that a very high price be paid for billions of unrighteous human lives. That price was billions of eternal human deaths. On the other hand, God wanted to give every human being the gift of eternal life, even though none of us deserved it, and even though His own high standards prohibited him from giving us that gift. But fortunately for us all, God found a way to offer all of us the gift of eternal life without violating His own high standards pertaining to who is deserving of that gift.
The Bible tells us that God did this by allowing His only begotten Son to pay for the unrighteousness of billions of human beings with His own life. But how could God consider only one death, a death which only lasted from Friday afternoon until the following Sunday morning, to have equal or greater value than many billions of human deaths, deaths which would last forever? He could do so because He considered the three days of life which His only begotten Son, Jesus Christ, gave up to be more valuable than many billions of eternal human lives. Why? Because God knew that Jesus Christ was far more than a human being. God also knew that Jesus Christ was far more than "a perfect human being," or "Adam's equal" as some of the cults like to call Him. God knew that Jesus Christ, as His only begotten Son, was also God. And because Jesus Christ was God, His Father considered His death, and His three lost days of life which followed His death, to be worth far more than many billions of eternal human lives.
Some have said that God requiring the life of His own Son to pay for our sins is an example of "primitive thinking." Is it? No, it was not. It was an example of His perfect justice, His great mercy and His amazing love. For the Bible tells us that God loves us all so much that He was willing to buy us all eternal life, even though to do so He had to pay for it "with His own blood." (Acts 20:28)