The dubious premise here is that this is anything like a wager where your choice of belief has any impact on the outcome and even that believing for whatever reason is all it takes to get the payoff. The reverse could easily be the case where the atheist doing what is right for its own sake is the greater display of faith showing he has the law of God written on his heart. I think this is more likely to have the approval of God than the person only believing and following some minimal set of rules because he thinks it earns some reward.
In other words the assumption you pin this on is just wrong.
That is not Christianity but Gnosticism and legalism… a gospel of salvation by knowledge and works. It is the kind of religion that people invent in order to use religion as a tool of power – believe and do what I/we tell you and God will reward you otherwise God will punish you. Jesus accuses those doing this to be of the devil and indeed that is the kind of bargain you would expect of the devil – the kind of bargain you get with organized crime.
So you can do the math this way…
God exists, you don’t believe, but doing what is right for its own sake gets the highest rewards.
God exists, but you believe because of Pascal’s wager so get the worst results.
God does not exist and you do believe then you live a stressful life fearing a nonexistent threat.
God does not exist and you don’t believe so you have the peace of mind that death is the end and absolutely nothing to worry about.
So I can assign benefit values (rationally scaling everything to a +/-100 scale): +100,-100,-50,+50 Then your calculation of the expected result assuming equal probabilities is: belief -75 (poor expectation), disbelief +75 (good expectation).
It seems pretty straightforward to me that only an extremely gullible person would buy into such claims of probability and rewards… the kind that buys gold mines in Atlantis.
Atheists are demonstrably rational and they clearly do not become Christian and that would be because they not so gullible as to accept the claims about Christianity being more probable than other religions let alone that any of these religions can really deliver on their promises.
Just have to argue that the Christian God will send to hell those making salvation into a wager like this, looking more favorably on those who don’t believe but do the right thing anyway. The kind of God spoken of in Isaiah chapter 1, Romans chapter 10, and Matthew 19.