Someone once said.. "Salvation costs us nothing, but discipleship costs us everything" To preach salvation without the call for discipleship, will be a compromise to Christ' great commission. To preach discipleship without the assurance of salvation, will be like preaching Christ minus the cross. One approach will be convenient, the other approach is virtually impossible. It takes His only Son's life to bring us salvation. It takes our entire life to live a disciple life. Both are costly, and only when both combines.. it becomes Gospel.
Yet God has made everything beautiful for its own time. He has planted eternity in the human heart, but even so, people cannot see the whole scope of God’s work from beginning to end. (Ecclesiastes 3:11)