Does it pay-off to be a follower of Jesus Christ? Is it a sound investment? A good decision? Can it be justified in the light of what it costs a person? These are the questions that make up the cost-benefit analysis of discipleship.
And this helps us get at the heart of Jesus’ words on discipleship in Mark 9:42-50:
Whoever causes one of these little ones who believe in me to sin, it would be better for him if a great millstone were hung around his neck and he were thrown into the sea.  And if your hand causes you to sin, cut it off. It is better for you to enter life crippled than with two hands to go to hell, to the unquenchable fire.  And if your foot causes you to sin, cut it off. It is better for you to enter life lame than with two feet to be thrown into hell.  And if your eye causes you to sin, tear it out. It is better for you to enter the kingdom of God with one eye than with two eyes to be thrown into hell,  ‘where their worm does not die and the fire is not quenched.’  For everyone will be salted with fire.  Salt is good, but if the salt has lost its saltiness, how will you make it salty again? Have salt in yourselves, and be at peace with one another.
Just prior to these words Jesus had, for the second time, foreshadowed his imminent and inevitable suffering, death, and resurrection (cf., Mk 9:30-32). The cross is coming and with it salvation for all those who believe. And because Jesus practices truth in advertising, he follows predictions of the cross with lessons on discipleship. He wants us to accurately count the cost of following him.
So, let’s summarize what is, according to this text, the cost of discipleship:
- A commitment to not do anything that would cause a believer to sin (v. 42)
- A willingness to eradicate anything in your own life that will cause you to sin (vv. 43-48)
- A readiness to suffer (v. 49)
- A determination to be other-worldly (v. 50)
Now, let’s consider the consequence of not being a disciple:
- Would be better for this person to have a great millstone tied around his neck and thrown into the sea (v. 42)
- This person will experience hell, where the fire is unquenchable and the torment of judgment unceasing (vv. 43-49)
Now, let’s consider the benefit of being a disciple:
- Eternal life (v. 43)
- The Kingdom of God (v. 47)
According to this brief cost-benefit analysis it seems clear to me that the cost of discipleship is certainly worth it whether considered negatively or positively. In other words, the cost is worth it because of the horrific outcome of not being a disciple. And the cost is worth it because of the glorious outcome of being a disciple.
In Mark 9:42-50 Jesus is echoing, and elaborating on, the radical call of discipleship he made back in chapter 8:
If anyone would come after me, let him deny himself and take up his cross and follow me. For whoever would save his life will lose it, but whoever loses his life for my sake and the gospel’s will save it. For what does it profit a man to gain the whole world and forfeit his soul? For what can a man give in return for his soul? For whoever is ashamed of me and of my words in this adulterous and sinful generation, of him will the Son of Man also be ashamed when he comes in the glory of his Father with the holy angels (vv. 34-38).
Christianity will cost you everything. But Christianity will benefit you for eternity.
So what does this simple cost-benefit analysis tell me to do with Jesus Christ? Believe.