They're taken advantage of when it comes down to deciding a salary. It's a situation where an H1B has to take the lowball offer, or leave it and be completely screwed.
The lowball offer if it is not prevailing wage is illegal. They are not allowed to work for less (there is a specific clause just for this) , just like other employees. And if the lowball offer is not less it aint no lowball offer.
../i am the queen of everything.