Consider the rich young ruler and his answer to the Lord Jesus Christ. He mentioned that he had kept all the commandments since his youth. Any person who sees their sinfulness can only say, "I have not kept the whole Law." Jesus told the rich young ruler to sell everything which was to show to him the impossibility of keeping the entire Law without breaking at one point. Many people are just too proud of their own achievements that it becomes very hard for them to believe on the Lord Jesus Christ. If there is another high cost in getting saved, it's the high cost that you yourself have to give up your pride and self-righteousness aside from taking the risk that you might get disowned by your friends and family.
Romans 3:10-19 and James 2:10-11 declare the sad truth that nobody can keep the whole Law. The whole world is guilty before God. Even if you only broke the Law at one point, it has already offended the whole perfect standard of the Law. The problem is fallen humanity in their pride think that if they do more good than bad, they can certainly make it. It is no wonder why Ephesians 2:8-9 states that salvation is by grace through faith so no man could boast. Even the good works of the genuinely saved believer are not done in boasting but done in the spirit of gratefulness, humility and because Christians love the LORD God with all their hearts. There is nothing to brag about the good works and the Christian about self.
Galatians 6:14 says that there is no other boasting but the Cross of our Lord Jesus Christ. 1 Corinthians 15:10 says that is by God's grace that Christians are doing the best they can to live a holy life. 1 Corinthians 6:11 says that it is the work of God that changes the sinner for the better from the sinful lifestyle to serving God by the Holy Spirit and not by one's own effort. If Jesus did not pay it all on the cross, if I did not put my trust in Him believing He is the Son of God who died in my place, I do not even dare say that without it, I would be a real new man. Many people "change" but it is only on the surface but the Christian life starts on the inside then it surfaces on the outside in the daily walk of sanctification.