VTSAX is 4 basis points of expense ratio. There are others with 3 bps and Fidelity has one with 0.

Even at 5 bps on a billion, I think you'd be extremely hard pressed to do everything Vanguard does for you for $500K/yr.

I'm at least a factor of 500 away from having to consider this question, but if you told me it would cost me $500K to have one fewer critically important person on my staff to deal with, that would be a good tradeoff in itself.