I will be headed to Argentina in March and my outfitter has stipulated $13.25 for Argentinian national shells and $15 per box for imported shells. He also goes on to advise charges of $14 for 28 gauge and $15 for .410 shells (I assume he is referencing Argentinian shells for the sub-gauges).
You sound well qualified as a travel companion however that spot has already been spoken for by my wife. Actually a buddy and I bid on and won this trip at a DU dinner last spring and what we thought was going to be a great trip for the two of us for a reasonable price turned out to be something much different when our wives demanded to travel with us. The ladies will fly to Buenos Aires with us and occupy themselves with local attractions (shopping) while my friend and I fly to Cordoba to shoot for three days. I'm afraid that the real financial damage will be done by the ladies in BA. Oh well, it is the "trip of a lifetime" and I suppose the women have earned some right to participate for having put up with us over the years.
I look at things differently than some people. If you consider that they supply the birds it's not much different than shooting trap. Rio's, Gun Clubs and Top Guns are 6.00 a box wherever you find them. Add the cost of a round of trap at your local club and you can get to 12.00 a box to shoot them. It's not as outrageous as people make it out to be in my opinion. Doves have always been a friend of ammunition factories because getting 25 straight is a real feat and deserves some chest pounding along with a Tarzan call. Duane