The film Norma Rae and the book Holding the Line bring up political issues for us to consider, Why does a woman have to "look like a lady, work like a dog, and act like a man" in the workplace, and still end up with less pay for comparable work, exposure to sexual harassment, and disproportionately fewer high level positions, to which we must add the lion's share of responsibility for family and home? How did we get here? Is this right, fair, appropriate?
Even as more women began to enter the work force in past decades, their salaries were traditionally lower than their male colleagues with similar experience because many companies (and society) viewed a woman's income as simply being a "helper" or supplemental income to her husband's income. Men's incomes were considered to be the primary income and thus they deserved more pay. That is just one reason that some companies have used to justify the unequal pay.
I agree with post #2 that traditionally (and religiously) speaking, women's roles were not away from the home. Whether it goes all the way back to the argument that it was the woman's fault in the Garden of Eden is a bit of a stretch to me. I guess I think of it more as the traditional roles of men and women have shifted in some societies more drastically and much faster than in others. I actually think it could be better connected to the fact that women actually give birth to children. As a matter of biology alone, this sets a precedent that a woman was made to take care of a family and matters of the home.
There are many who still hold to this traditional and old fashioned view, who successfully hold back progress in societies which are moving away from traditional/religious foundations.
One of the reasons that women are paid less and work harder has to do with the common practice of keeping pay rates secret. If everyone know what he or she was being paid, that transparency would lead to some interesting discussions. The truth is we don't really know how widespread this practice is in our own organizations. Unless you have a strict salary schedule, women can be paid less while no one knows it. Even with a salary schedule, promotions can often go to men instead of women with little recourse.
I'd be surprised if you get anyone arguing that it's right, fair or appropriate...
As far as how we got here, there are so many possible reasons. One that you could mention is religion. The Judaeo-Christian tradition (among others) marginalizes women, blaming them, for example, for the "fall" of mankind. The Catholic Church (the only Christian Church in the West until the 1500s) does not let women become priests. There is the idea of women obeying their husbands that religion has tended to promote.
This cultural idea has kept women largely out of the workplace (especially in anything but menial positions) until very recently. Since women were not in the workplace for so long, a series of prejudices have arisen that lead us to the issues that you describe.
Of course, there are so many other ways to account for this. I'm sure you'll get others.