The GOLD ETF has a management fee of, I believe, 0.4% per annum. The mechanism for payment of this fee is by the reduction of entitlement to the amount of gold per unit ie. the units started off life as 1/10 of an ounce and are now equal to about 0.097 of an ounce hence a discount of approx 3% to spot. See entitlement schedule in asx announcement:
http://www.asx.com.au/asxpdf/20110303/pdf/41x6cwbbx6lfvg.pdf