Wirelessly posted (BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
Just use frequent-flyer miles for the one-way back from LIM. Depending on the day of travel, a Coach one-way can be had for as few as 15,000 AAdvantage miles (subject to award-seat availability, of course).
If you don't have AAdvantage miles, check the FT MilesBuzz! forum for the Citi/AA Visa card offer that yields 75,000 AAdvantage miles after charging $1,500 to the card.
In markets where one-way fares are very high, one-way frequent-flyer awards can often provide excellent value.