This story is boring. Another person complaining that he's underpaid, because he didn't negotiate. The fact that he had a job makes him lucky enough. He should be happy. Nevertheless, we've all been underpaid before, it happens to lots of people.
Why do you assume the manager is a woman? I've actually never seen a woman manager. If you're afraid of gender bias, why not petition the cosmetology industry to fix the female-centric gender bias? Men are under-represented in nail salons too..