it is also really hard to keep your net worth a secret when it's in billions.
I challenge you to give some examples of people who've got that rich (legally) yet kept it a secret.
I challenge you to give some examples of people who've got that rich (legally) yet kept it a secret.
The literal interpretation of the challenge is a paradox. The contradiction is that a secret is no longer a secret once revealed (hence my comment).
I don't think that is what you were trying to convey. You do raise a valid point, but without any supporting evidence, it is thoroughly unconvincing. The absence of X is not enough to conclude that X does not exist (especially when X is being purposefully hidden, as in this case).
NOTE: I am not disagreeing with you. I don't know whether or not secret rich people exist.