He apparently has a hard time looking professional, neat, clean, and tidy. Must not be an Eagle Scout
..."A scout is...clean"
My other thought is that I couldn't ever see myself wearing a suit every day to work, which is partially why I am self-employed and I can dress however I dang well please.
My last thought is that if you require him to wear a $1,000 suit, is he interviewing for a job that will pay for a $1,000 suit? I mean, if he's looking for $50,000 a year and you want him to wear a $1,000 suit, I'd personally tell you to take a hike and walk out the door. If he's interviewing for $100,000 then he should expect to dress the part and if he doesn't own a $1,000 suit he should have said he's more than willing to go pick up a few if it is required of him, which it sounds like it is.
All in all, I don't think this has much to do with the fact that he's a mormon, just uneducated in interviewing techniques. It probably reflects his personality and upbringing more than anything religious.