Every one of those pages is absolute bunk with made up numbers. They're trying to drive clicks. Take a look at any of them and you'll notice quite quickly that they never cite any source.
> take into account known salaries, real estate holdings, divorce records, royalties, lawsuits, and endorsements. Our estimates incorporate a proprietary formula that removes estimated taxes, manager's fees, agent fees, and lifestyle expenses. The results are fact checked and confirmed by a team of editors and industry insiders.
No idea how truthful or accurate this is, but $20M does not seem unreasonable. Are there any better sources you know of?