Now you can argue that postdoc and research positions don't pay well enough to attract local talent[1], but I don't think you should conflate this issue with the typical Indian consultancy companies working their way around H-1B constraints.
[1] Which seems true from what I've seen. I know people at the Berkeley Lawrence Lab who would triple their salaries working in the industry.
To hire somebody via H1B route, you need to: a) pay at least average salary for this position; b) prove that there are no local candidates available for your opening, c) prove that it is not because of your low pay rates, but because of genuine shortage of specialists with these particular skills, d) pay processing fees and wait for at least 6 months, perhaps more.
Common sense says if someone cannot freely move between jobs, who faces immanent deportation if fired, who will have much better prospects of living well in US than their home country, then this person has much less leverage and would be paid less. It is easy to test this hypothesis: do H1B holders have a much higher rate of changing jobs after obtaining visa than their peers.
Come on now. You can't actually believe this is how it works in real life.
http://www.cringely.com/2013/07/18/so-thats-how-h-1b-visa-fr...
>> The EPI study, written by University of California-Davis computer science professor Norman Matloff, compared American-born college graduates holding degrees in computer science and electrical engineering to their foreign-born counterparts.
>> There are, of course, reasons for this that have nothing to do with intelligence. More than 80 percent of H-1B visa holders are approved to be hired at wages below those paid to American workers for comparable positions, according to EPI. And because H-1B workers and green card applicants are locked into jobs with whatever employer sponsors their visa, they have less less leverage to push for raises and promotions. As Matloff puts it, "the worker becomes a de facto indentured servant."
http://www.motherjones.com/mojo/2013/02/h1b-visa-bloomberg-f...
Also:
http://www.motherjones.com/politics/2013/03/microsoft-stem-e...