If the supply of those interpreters is so limited that you have to go outside of the U.S. to find them, then doesn't supply/demand indicate that they should have a high salary?
Edit: This is how H1Bs should operate according to their stated purpose. edge17's link to http://www.myvisajobs.com/Reports/2017-H1B-Visa-Category.asp... shows that it's not being used in this way at all.
Supply and demand curves are (a) curves, not two points on a line (b) curves as a function of price. You can use them to pick a price, but not to come up with one from amounts of X ex nihilo. Even if we're sticking with the most primitive micro-economic theory here, you've discarded a whole dimension.