Unfortunately, it isn't about gender equality. Soccer clubs are businesses, so renumeration is dependent upon potential, or actual, contribution to the revenue stream - be that gate receipts, merchandising, TV rights and so on. So, for the Manchester Derby there would be 75,000 in the stadium. For the women's Manchester Derby, maybe 2,500. The English Premier League has the most in-demand TV rights in the world, behind subscription paywalls, in many countries. The women's game is generally free-to-air,with only a fraction of the audience for the men's game. Once the women's game is as lucrative as the men's then they will be paid accordingly.