If an employee costs the business £3,000 a month, they do not necessarily need £3,000 of extra sales. If only 40p of every extra sales pound remains after the direct cost of doing the work, the business may need around £7,500 of extra sales to produce £3,000 of contribution.
The role may create value without directly selling
A cleaner, administrator or operations hire may free the owner to sell, reduce overtime, prevent lost work or improve capacity. The calculation is still useful because it tells you the size of the value the role needs to create somewhere.