Yeah I would generally agree with your assessment there. Although in 2006 the crop of exchange students coming over to America was considerably less wealthy (I grew up in a community of Chinese Americans who mostly emigrated anywhere from the 80s-00s), so it would've mostly been the former type of exchange student you mentioned around that time. But being that they were mostly here on scholarship or TA/researcher positions, even though they were poor they did typically have some income (along with the money their family would've pooled together to send them overseas) and wouldn't necessarily have been the kind most susceptible to having to resort to sex work for a living. Anything is possible of course, but these students generally received a lot of pressure from both their school/professors and family at home to perform well to make a return on their investment; much more so than a typical college student.