Materialists claim that the believer in God, exactly like the atheist, is motivated by self-interest, because they expect to be rewarded a great interest, an eternal paradise after death. 

However, this materialistic analysis is illogical, why? Because the logic of interests is strongly connected with the near time, and without this closeness of time it won't be called interest. The closer the fruit the more it becomes an interest, this is the logic of interests, like when you put a land for sale and announce that its price will be doubled after 5 years, you'll find many people wanting to buy it, but if you say it will be doubled after 15 years you'll find less costumers, and if you say after 40 years they'll be a lot less, and if you say after 70 years they'll laugh at you, and if you say it will be doubled after death they'll call you crazy! 

This is the logic of interest, which is entirely inapplicable to the idea of paradise in the afterlife, after we all turn into dust and the whole world ends. Notice how fragile the connection is between the believer in God going to heaven and self-interest, which makes the whole idea unconvincing as the rest of the materialists' analyses.   

According to this idea, there is no value for the love of God after the believer goes into heaven and survives hell, all the love will be poured into heaven! This is logically unacceptable. And according to this idea, after believers in God go to heaven they won't love God because who enters paradise will not be taken out from it! Doesn't this make us doubt the whole materialistic analysis and its inconsistency with reason? 

Thus, the law of self-interest isn't what motivates the believer in God. They are moved by a moral motive which is the love of God, and the love of the existence of the God, because He is a symbol of good. The true believer in God adopted their faith because they love good and is ready to sacrifice their interests for the sake of good, which opposes the law of self-interest. The true believer is even ready to sacrifice what's called the guaranteed interest. So is it logical, according to the logic of interest, to sacrifice a guaranteed interest for an unguaranteed interest that only comes after the end of the world and the whole universe?  

Many believers in God, but not all of them,  do try to join the two ideas, in that they want paradise and yet they don't want to sacrifice their self-interest, but that's a contradiction caused by their preference of their self-interest. Therefore, the idea of self-interest corrupts faith, and a thing can't be built on what corrupts it.