We cannot earn, or sell, what is free.  However, we can and should be mature enough to value a free gift that comes to us at a great price by someone else.  This is love: not that we loved God, but that he loved us and sent his Son as an atoning sacrifice for our sins (I John 4:10). 
 
We cannot and did not initiate God's love for us.  God loved us because He is love.  And, if we did nothing to get God's love... we can do nothing to get away from or to lose God's love. 
 
Our commission is not to sell the Christ or convert people to Christianity.  Our mission must be to inform people of Christ's love and the atoning work of salvation, and relaying to them that His work of salvation is both finished and free to us!  Do we pay for a gift or only receive it?  Isn't the essence of a gift that it is given?  And what an amazing gift it is!  Let's not go to the "salvation superstore" and attempt to pay for something that has already been purchased.  Christ has paid our debt in full.
 
Salvation does not happen when we accept it.  We only awaken to a salvation that has already happened.  The gift of salvation has been given to the world.  Our mission then becomes to inform that world so that they may awaken to the wonder of that gift.