Agree with the AC above.
This issue is not unique to textbooks. Software sales in Australia are inflated. Labor rates for engineers in India are increasing (and correspondingly, some of the pay rates or demand in the US is flat-lining).
even worse, it prevents them from doing things like giving away their textbooks in africa at a loss.
1) Charity should not be factored into Supreme Court decisions.
2) I highly doubt Wiley is using a significant chunk of the US profits on book sales to give away free books in Africa. But, if they are they are free to donate money and goods as easily as anyone (or any corp) can, and correspondingly write that off their taxes. It's up to me as a consumer to decide what I want to do with the money I save; I am certainly not going to look out for Wiley's interests. Maybe I will put the rest into a charity that I think will get it done better than Wiley?
The company I work for manufactures low quantity, high cost widgets around the world, and also sells them to different markets. Guess how long it would take for customers to figure out which of our branches will net them the best deal? Our manufacturing costs (and quality) vary greatly around the world. As a company, we average it all out.
To your specific example: If Wiley is selling textbooks at a profit in Thailand, then they should be able to sell the same textbook in the US (also at a profit) for around the same cost. Let the students decide if they want to pay $100 extra a hardback, or whatever other "features" they perceive. If Wiley was smart, they would cut out the eBay market for international-version textbooks and sell direct to students.
My prediction for the future (other than e-books as other commenters pointed out): Bundled one-time activation codes to a website or software that comes with a new book, like a DLC for the used games market.