I've seen this said a bunch of times but never anything to actually back it up.
The fact that big pharma companies tend to have fantastic margins and spend similar amounts on R&D as they do on marketing makes me think that it's probably bollocks.
The idea that big pharma companies are happily scalping Americans just so they can provide drugs to countries that can't actually afford them is just... absurd.
Here is a recent blog post that has some references to economics research papers around this general topic, but likely not directly addressing your exact claim. Nonetheless, you may find it interesting: http://slatestarcodex.com/2016/09/07/reverse-voxsplaining-br...
The idea that big pharma companies are happily scalping Americans just so they can provide drugs to countries that can't actually afford them is just... absurd.