Christianity is cheaper.

I laughed inappropriately the other day when I was at the interview of one of the first believers in a Pwo Karen village in the mountains near he border of Thailand and Myanmar. I laughed because they said the main reason why they became Christians was because it was cheaper than being animist. I'd slipped back into a Western mindset and was expecting an answer that revolved somewhere around the guilt/sin paradigm and some deep repentance, so this just caught me off-guard and I giggled.

It makes sense though. Animists have to frequently sacrifice animals to appease the spirits and so when this became too much of a burden for them, they turned to Christianity because it didn't require any animal sacrifices, and instead taught that Jesus was the already completed perfect sacrifice. 

After this, I heard my pastor was recount his experiences in Borneo sharing the gospel with an unreached tribe there. He sat quietly and talked with the headman of the village who was mainly fascinated with the idea that they would no longer have to sacrifice an animal every morning in each corner of the village for protection, as their shamans taught. By the next morning that village had become followers of Jesus. 

So is turning to Jesus out of economic need a bad motivation?

I don't actually think so. In Hebrews 9 the Bible makes a fairly big deal about how Jesus 'offered himself to God as a perfect sacrifice for our sins' (v14, NLT) and superseded the OT laws of animal sacrifice, where 'the blood of goats and bulls and the ashes of a young cow could cleanse people's bodies from ritual defilement' (v13, NLT). I think it's just the way the Gospel is preached in the west does not emphasise the sacrifice of Jesus as anything more than a symbol, perhaps dealing with inner conscience, because we don't practice ritual sacrifice as a lifestyle. So we read it as a historical, almost symbolic story and skip over the blood, gore and money that it takes to procure animals. But it was important to people in the time of Jesus who still sacrificed in the temple in Jerusalem. And the Bible is relevant to all people, through all ages, and quite conceivably, God knew there were tribes to whom it was very important to hear that Jesus replaces actual, physical sacrifices even today. 

So can we preach something like this? 

Turn to Jesus, because it will save you all the expense of all those bulls/goats/chickens you sacrifice to spirits who give you lesser protection than the Son of God who died once and for all your sins/curses?

Sure! Why not? As long as we don't leave it just there, I think it's as valid as any other explanation of the Gospel.