It's impossible for the price to fluctuate higher or lower than the underlying NAV. The ETF provider has to provide constant buy and sell amounts for a small spread around the NAV, so for example in the case of the INDI, satrix has a standing offer of 25000 on offer to purchase for around 6c more than NAV, as well as a standing offer of 25000 to sell at 6c less than NAV. And then when you buy a portion of those, say 5000 for example, it'll only be a few minutes that you see the shares for sale sitting at 20000 before they top it up again to 25000.