I'd go for the cheapest RT tkt since it is high season. Some things are worth the money! After all, we sure don't pay much for our long haul flts.
We bought tkts from CDG to Malta but ended up doing ezeds on return since the flt was wide open. I was prepared to buy rev tkt but unnecessary. We expected to do the same w/Iguazu Falls but it was off season so we did the zeds.
Or you could do like my nephew did and buy a motorcycle, ride from Santiago for 5 months in Patagonia, then take it back and sell it!