See this Twitter link to a blog post from my colleague, Mark Ashwill, based in Hanoi: http://wp.me/pI5NK-1li .
He writes: The total economic impact of the nearly 15,000 Vietnamese students in 2010/11 was $416 million using information (PDF download) from NAFSA: Association of International Educators. This is an extraordinary sum for a country at Vietnam’s stage of development with a GDP of just over $120 billion in 2011. (In case you’re counting, the estimated amount spent on study in the USA by Vietnamese families last year equaled .35% of the nation’s GDP.)
Since the above Open Doors statistics include only regionally accredited institutions of higher education and exclude other Vietnamese enrollments (e.g., nationally accredited schools, private boarding schools, most of which are in the 40-50k per year range per year), the total economic impact is considerably higher.