I also see US$70 popping up on IATA, but this is for tickets issued in Chile, so you would probably need to contact a local travel agent to obtain a ticket at this price.

When I change the "Sales City" to any US port, the price rises to US$86.

While I already think this is a pretty decent price for a 4-flight, and is already a third of the next-cheapeast non-stop fare, if you want to find a lower fare, then you probably need to use a price-comparison website and hope that some agency is willing to undercut the others and save you a few more pennies.