> It doesn't need to be high, though, since the risk and reward is so high (failure means more lost, success is a life).

I think the risk:reward is often seen as higher than it should be even given the "going to hell" assumption, because the failure cost of the attempt is seen as capped at zero because alienation is not considered. This might make sense in a context where your particular door-to-door attempt was very likely to be the only exposure to Christianity that the target would ever have, but (since alienation of an unbeliever in that case would have the same effect as not making that particular door-to-door conversion attempt), but somewhat unlikely in the modern world.