This is the first time a security detail for Sandberg has been reported.
According to the company's latest annual proxy statement, $4, Sandberg made $715,385 in base salary, a $1,265,193 bonus, $15,465,667 in stock awards, and $1,252,724 in "all other compensation," for a total pay package of $18,698,969.
To explain that "all other compensation," Facebook says in that document:
Our compensation & governance committee has also authorized a security program for Ms. Sandberg, including certain personal security measures, to address safety concerns resulting from her position as our COO. We require these security measures for the company's benefit because of the importance of Ms. Sandberg to Facebook, and we believe the costs are appropriate and necessary.
It's not 100% certain that the "all other compensation" consists entirely of the cost of Sandberg's new security detail. But it's worth noting that in 2013 and 2014, years before Facebook apparently decided Sandberg needed professional protection, that same column shows that she didn't get any "other compensation" at all.
Sandberg isn't the first Facebook exec to get this kind of treatment: $4, as well as a $4.
That said, Facebook's spending on Zuck's security apparently declined from $6,213,106 in 2014 to $5,037,840 in 2015, per that proxy filing. The difference there just about covers the new cost of Sandberg's security detail.