Psychic profits are still profits. When someone donates $5 to a homeless person, it's not because they expect a monetary profit; it's because the psychic/emotional profit they get (helping someone else) is worth at least $5 to them.

What I've never understood about non-fanatic religious people is why they don't go 100% in. On one side of the balance, you have eternity. On the other, some integers. Infinity is always going to beat some integers. I understand the suicidal jihadist way more than I do the Sunday church-goer who puts $5 in a basket. Why not $500? Why not 5 million? Why aren't you living as a missionary in a tent, giving up all earthly possessions to maximize returns times infinity?