After spending my life in overwhelmingly male-dominated workplaces, I found myself surrounded by women when I started freelancing. And when I got involved in hiring writers, I noticed something. Every guy I hired asked for more money. None of the women did.
It became a running joke between me and my (female) client. Especially because I asked for more money when I first started too.
But you're dead right that this is a mindset. Call it internalized misogyny if you want, but it's on all of us to take care of ourselves. The only thing stopping a female freelancer from asking for more money is the freelancer herself.
Of course, what I have between my legs precludes me from writing articles like this. But I'm glad someone said it!