> For same responsibilities same salary. Why is that? If there is someone who is willing to take on those responsibilities for less pay, well that's just fine for the company and I think that people tend to forget that Google (and many other IT companies) is a for-profit company.

For me at least, I've always seen salary negotiations as somewhat of a "right person at the right moment". If you're very lucky and the company really needs they will be willing to pay you more than what you would make at a different company on the same role, maybe more than what others are doing on the same role, just because you were there, at that time, when they were most in need. It may not always be like that, but think of it as demand/offer relationship.

So regardless of gender/race it's the need of the company that comes first. Because as a employee you fulfill a need that the company has and you are being paid for that.