I think it's really tricky for a jean to justify a high pricetag, simply because there is so much competition in this market that you will always find somebody else who is doing something similar at a more attractive pricepoint.
Then again, if you succeed in offering a unique product or if you manage to put a very personal stamp on a jean (and by that I don't think of fancy rivets as with Nina Ricci, who are asking for more than 500€ for theirs!), there is no reason comparing them with another regular staple pair that you probably got for a lot less.