This problem is unique to LA who is very stingy in offering any discounted seats on any basis (not just OWE). They go on the plan of selling 90% of the plane for full fare, and flying empty when it doesn't happen. The SYD route is particularly bad as there are so few seats per week and so few alternative routings (though OWE allows routing via LAX, for example, as long as you have purchased NA as a continent -- so you always have that option, using any North American transit to get to SA). Given that you are flying economy you would be better off to fly SYD-JFK-EZE, for example, instead of SYD-SCL (lots of other alternative routings).