I'm not going to defend Mormon beliefs, but I will play devil's advocate. Many Mormons view tithe as giving back to the community of which they're a part. And that community, they believe, will provide value to them, in turn. And generally, it does... as far as I can tell from the outside.
I'll also play devil's advocate and suggest that perhaps some people also get value from their psychics. As far as I can tell from the outside, some psychics essentially serve as life coaches for their clients.
And just as some people find religion comforting with regards to their passed relatives ("I know Grandma is in heaven!") others may find similar comfort talking to Grandma via a psychic -- even if both are total fabrications.
One additional difference is that the psychic is being personally enriched by the money, whereas the Mormon leaders are not being personally enriched. (At the highest levels they get a stipend, of around 120k/year last I checked). Now this is not true of other churches necessarily, but it is true of the Mormons.
