As for your source -- how about common sense and the most basic econ 101 chart on supply, demand and price? http://www.investopedia.com/university/economics/economics3.... The higher the supply the lower the price.
Hardly sounds like they're being exploited and suffering due to a glut in supply. Either that or "exploitation" rates in the US are double the market rate in Canada/EU.
(That said, I've seen startups in Toronto offering $50k/year lol!)
Since you do bring up salaries though, after taxes, health premiums, co-pays, 75 will get you a shared 1br rent in SF. If that is good for you, great. Don't say it "should" be good for everyone, it isnt. We live in a market economy, so everyone needs to play by the rules, not try to justify market manipulations with "well, oh, that should be good for you."
Absent government interference, that includes supply and competition from foreign workers who, surprise, by and large do not feel exploited making more in a year than their parents back home make in a decade.
Of course foreign workers dont feel exploited -- if they did, they would not come here!