obviously the lion share of their net worth is gonna come from endorsements and partnerships over their career purses/fees. so no doubt white/male privilege is gonna come into play. but there are some other factors at play too.

mens tennis overall is just a bigger draw with a larger consumer base (men buy more athletic apparel, equipment, etc). plus federer has high profile rivalries (rafa/djoker) that consistently draws in a ton of interest/ticket sales/ad dollars/etc.

and dont forget tennis is a sport with an international audience and consumer base too. as big as serena is to american tennis...federer is most likely a bigger star in a lot of overseas markets. japanese company uniqlo signed him to a huge deal a while ago that even nike couldnt match.

if you can sell products across the entire globe then companies are gonna offer you more money (look at soccer stars).