Magnum bottles are priced more than twice the price of regular bottles in Australia. Is this justified?
In the old days, when wine was bottled under cork, the argument was that you could cellar a magnum for longer, as there would be less oxygen exposure per unit of wine. I have found this argument to be true, by and large. Therefore for people who cellar wine, this was additional value. Another argument is that costs are higher due to much lower volumes, in particular for glass bottles and labels. However, most magnum bottled wines are premium wines, and the additional cost, if any, would not have been high as a percentage of sales.
These days, many wines are closed by screw caps or twist offs, including ultra premium wine. There is no advantage in cellaring these wines in magnums. The only other potential benefit is ceremonial. Presenting a magnum to a group of people could be construed as more festive than 2 bottles of wine. Personally, I don't think there is much in this.
I conclude there is no longer any justification for the premium price of magnum bottles.