I also wanted to look at net worth as a measure of value outside of prize money alone.
If we deduct actual prize money from estimated net worth we get a more holistic picture of how Serena is valued. Let's compare with Federer, Nadal and Djokovic who are arguably 3 of the 5 greatest players ever and have combined to create an era of mens tennis that is without question the greatest ever and probably the greatest and most competitive era in any sport. It's akin to LeBron, Jordan and Wilt at their primes going head to head.
Federer NW = 450 million, less PM of 130 million = 320 million "non-tennis specific worth"
Nadal NW = 180 million, less PM of 120 million = 60 million "non-tennis specific worth"
Djokovic NW = 220 million, less PM of 144 million = 76 million "non-tennis specific worth"
Serena Williams = NW 200 million, less PM of 92 million = 108 million "non-tennis specific worth"
Hmmm, numbers don't quite add up to the claim do they. The only area Serena Williams can legitimately be upset about "not being valued" is with her career prize money but of course since 2007 the prize money at grand slams (the majority earner for tennis players) has been equal for men and women - the only sport to do this, and 16 of Serena's 23 grand slams have happened in 2007 and later with equal pay parity.
Not sure how you take an objective step back and make the claim you are undervalued and underpaid - unless of course you live some sad and oddly pathetic existence where you live in a cycle of trying to prove you are constantly a victim of something that may exist within your mind and not reality.