Point of sale can make a difference in the fares that are available. If Argentina is cheaper but you're doing the purchase, I'm not sure you can get the foreign point of sale--this might depend on the airline.

Argentina *might* be considered a risky origination point for fraud. The passenger might be asked to present the credit card at airport check in that was used to purchase the ticket, or you might need to do some additional authentication step in advance of the travel, possibly in person at an airline ticket office. It could be more complicated if you use an OLTA.

Could you instead just reimburse the friend for the cost of tickets or possibly pay for lots of stuff (lodging, attractions, local transportation, meals, drinks) at the destination to avoid a transfer of money?