just wanted to share how this story ended, hopefully one day a nomad will profit from this experience:
First I checked with Apple if there is a international warranty. There is and I even can purchase a protect plan back home for my chilenean MB.
I went on a awesome three day tour through the salar uyuni, which offered an option to end up in san pedro de atacama in chile. From there I made a day trip to Calama, an ugly city with shopping centers full of apple products!
of course the MB 13“ i wanted was sold out in the mac online store, so i headed over to reply and taddaa, they had one left - for a discounted price.
in the end the mb air was cheaper as in switzerland (<1000 usd), the flight to buenos aires ended up to be 150 usd less than from sucre and i had the chance cross the salar flats without an extra effort. and if the insurance will pay, i just replaced a four year old laptop without paying for it. conclusion:
a) if you need apple products in south america, chile is the place to go!
b) if shit happens, try to turn it into an opportunity