It's 'only' ~$50M or so [0], per what I could find with a quick googling. Other resources would be appreciated though!
[0] https://www.wealthypersons.com/paul-graham-net-worth-2020-20...
[0] https://www.wealthypersons.com/paul-graham-net-worth-2020-20...
3% of that would be nine billion, assuming all four YC founders had equal shares and disregarding dilution as the portfolio companies took on more investors.
Likely off by an order of magnitude in one direction or the other but still fair bit higher than 50 million.