Salvation is a gift, but it costs something. God gave us the gift of eternal life by believing in our hearts and confessing Jesus Christ as Lord with our mouths for salvation (Romans 10:9-10).
When you got reborn, the day you confessed Jesus Christ as Lord and believed in your heart that God raised Him from the dead, by faith, and repented of your sins did it cost you anything?
Paul realized the price of redemption and the gift of eternal life through Jesus Christ when he called himself a bondservant (Romans 1:1). Oxford dictionary defines a bondservant as a person bound in service without wages (a slave or serf).