Melbourne to Buenos Aires?

[Tortuga]

I need to book a one way ticket from MEL>BUE for early October. I have done some searching and found Qantas to be the cheapest and most direct at $1500 AUD. I only have 16,000 points and was thinking of using points+pay to reduce the cost down to ~$1400 AUD. Since I know you guys and girls are experts is there a better option than the one I see? Maybe buying points and booking an award? I have no idea, just want to make sure I am making the right decision. I also have 55,000 miles with united however I can't see any way I can use those points since none of the star alliance carriers fly to South America from Australia or New Zealand. Appreciate any help