I would never pay over 50 dollars for a pair of jeans, much less 400 something, that's just rediculous. The most I'm ever willing to pay for a good pair of pants is in the forty dollar range, but most of the time I wait for them to go on sale and get them at around 20. What can I say, I'm on a college budget and like to save my money when I can.
However, even if I had more money than I knew what to do with, I still would not pay that much for a pair of jeans, nothing you could do to them would make them worth that kind of money.