This is a common but silly claim; there is, generally speaking, no such thing as a safe rate of return that overcomes the inherent losses due to inflation. If you're getting a 5% rate of return on cash, that comes with both risk (someone with a billion dollars isn't going to benefit from FDIC insurance) and doesn't even overcome basic inflation.

That $50 million a year is also subject to income taxation and cannot be easily avoided. $50 million a year in interest on returns from cash will be hit at the 37% marginal rate, plus whatever the state assesses, so north of 50% in California.