Does Relic Crown do anything else than sell for a high price? I mean, you have to go through Relic castle, and all you find is a item that sells for maybe $100,100.
No, it does not have any use besides getting you a lot of money.
The only thing that the Relic Crown does is give you 100,000 PokeDollars when you sell it to a man in the Undella Mansion (think its what its called). Other than that it just takes up space in your bag! LOL