True, but how often do you hear people here complain about CEOs making millions? Either it's related to effort "He's golfing with vendors and reading trade magazines while I work my butt off 60+ hours a week" or results "I've created millions in revenue for them and after 20 years they lay me off and outsource my job to India." Does anybody tell you to STFU, take an MBA and become a CEO yourself? No. But if a nurse complains about long shifts and crappy pay for saving lives then it's easy to pull the same card and say if you wanted to become an engineer, well you could have picked a different career. If you want to argue that the free market hasn't provided you with a pay equal to what you're worth that's fine, just don't be a hypocrite when others do it too.
Your pay is basically as much as necessary and as little as they can get away with, if the job is important or not doesn't really matter only the price of your replacement. That's why they made minimum wage laws, otherwise they'd have people underbidding each other until they were all working for pennies. It's nice when you're on the upside having a rare skill that's unexpectedly in demand and can command a fat pay check, but if you think your real worth to society is so high because you can make big money throwing a football in NFL or writing HFT routines for Wall Street you're wrong.
How does sex tie in to this? Well, according to feminists the reason "female" professions is paid so low is because the jobs are being systematically undervalued compared to equivalent work dominated by men because the executives - that are mostly men - can get away with it. Kind of like the two wolves and a sheep story, except the wolves are just deciding sheep work is worth less, if you want wolf pay you must do wolf work. Note that in many of the "female" professions like grade school teachers or nurses there's no direct economic output. What second grade math is worth is largely what society's perception of the value is. It's a lot easier to say that without this developer we can't deliver this product that'll create this much revenue.
I'm not saying that there actually is a problem, but it's not an open and shut case. Since it's inherently comparing apples and oranges I guess there'll never be absolute truth. I think it happens with minorities though, for example in cleaning services because the language requirements are practically none. If companies more-or-less collude to depress prices, they can squeeze out the natives which get better paying jobs elsewhere while the immigrants have very little choice but to keep working. Is creating such an ethnicly-dominated, extremely low paid underclass racism? Or reflection of their lack of work skills? I'm inclined to go with pure captialism, if women can't/won't leave "their" occupations that will be exploited to pay them less.