How effective is Christian outreach and how much does it cost?

As a Jew, I'm not very familiar with the concept of evangelism, but I was wondering recently about the cost of conversions and how effective they were. Unfortunately, I couldn't find any answers to my questions online. So here they are: - What percentage of attempted conversions succeed? Like, if you try to do outreach to a group, what percentage of those people will convert? - Is it harder to convert someone who's religious in another religion as opposed to a nonreligious person, and if so how much harder? Do different religions have different rates of conversion success? - Do different Christian denominations have significantly different conversion success rates? - How much does it cost per attempted conversion (if you outreach to a group this is the total cost divided by number of people in the group)? I'm not really sure where to ask this but I thought this might be a good place given that some people here have likely done missionary work before.