Why did God have to pay a price of redemption for Israel and the world?
Redemption was necessary because both Israel and the world were once God's possession but were lost through sin. Satan took control, holding them until God paid the required price to buy them back. That is why Scripture speaks of being justified freely by His grace through the redemption, the process of buying us back.
Les explains that redemption means buying us back, and the word must be used because you do not buy something back unless you first owned it and lost it. Everyone, Jew and Gentile, rich and poor, has sinned and come short of the glory of God. Verse 24 says they are justified freely by His grace, and God justifies through the redemption, the process of buying us back. Les uses the illustration of a hock shop: something was yours, you hocked it and took a loan against it, and the holder controls it until you pay the price of redemption. So in Scripture, God had to pay a price of redemption first for Israel nationally and for the whole world in general because that which was once God's, He lost. Satan picked it up and holds it tight until God pays the price. Israel was lost when the brothers sold Joseph into slavery; it was sinful and wrong, but God lost control of the little, still-embryonic nation. They ended up in Egypt and were under the Egyptian yoke for 215 years, until they came out as recorded in Exodus.