I've worked for two companies that used H1B visa workers, and I knew what they were being paid. Their salaries were in line with domestic workers in their positions. Now, my experience is based on a small sample size, but in talking with those employees about the H1B and their related experiences, I didn't come away with the feeling that these employees were being underpaid. But again, that's just based on my personal experience and what I've been told by employees in that program.