Spiritual capital is a form of wealth. In the end, you have no way to know wether someone is truly faithful or not. I recently learned about this passage in the bible, where Pharisees are like cups. Clean from the outside, but inside, full of sin and unclean. Someone could give up his millions to pretend finding spirituality, and be lying about it. I agree with you in a sense, you have to willingly give up material goods to gain spiritual capital. But still, your wealth remains unchanged, and you had to have some wealth to begin with. Same goes in the other way, if your cup is clean even from the inside, it will shine through life and compound, with relationships, opportunities, and maybe loop back into material capital.