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.
"'I beg you, father, send Lazarus to my family, for I have five brothers. Let him warn them, so that they will not also come to this place of torment.’ Abraham replied, ‘They have Moses and the Prophets; let them listen to them.’ No, father Abraham,’ the rich man said, ‘but if someone from the dead appears to them, they will repent.’ And Abraham said, ‘If they do not listen to Moses and the Prophets, they will not change and repent, even if someone were to rise from the dead.’” Luke 16:27-31