It’s interesting to do the calculation for one’s own work.

It’s obviously going to be flawed unless it’s a very basic job. The peripheral costs are the devil. Eg: Stationary, payroll costs, uniform, software licences, swipe cards, coffee, water, rent.

However mine is an awful lot higher than the CEOs (as a percentage, not in dollars).

I don't think the peripheral costs are even the bulk of it. The real value of the company is problem selection, brand recognition, coordination, hiring, and elimination of non-value add problems (e.g. an early stage CEO spends a huge amount of their time managing government registrations, which is later managed elsewhere in the company but not by 99.999% of employees)