Why do CEF and GTU carry such a premium over Net Asset Value?
Because this is the premium people are willing to pay for what they perceive to be 'real bullion' versus 'paper bullion.'
GLD tends to have a negative premium because it is a vehicle for traders, and particularly short sellers.
Deviations from NAV in themselves mean little, if the deviation is steady. It is in the fluctuations that information, and opportunities, are discovered.
"You are the very cause of your ignorance, yourselves. You put away the light, yourselves; you first pluck out both your own eyes, yourselves; and after that other men’s too, so that the blind may lead the blind, until you both fall into the pit.”
Thomas More, The Sadness of Christ (Gethsemane), Tower of London, 1535