Mark won't be paying any income tax on the cost of that security detail.
And a lot of things are vaguely related to security in some way, so can be put on the security budget.
Because that's what some of these CEOs are - in fact I dare to say that the order of public perception for a lot of these individuals are: celebrity first, CEO of something something second.
Must be head of state level security these guys use.
1- https://www.pbs.org/newshour/politics/us-pays-2m-a-month-to-...
I don't like Musk as a person, but if he died I'd be worried for SpaceX and Tesla.
On the other hand, losing Facebook would probably improve the world.