You might be comparing apples and oranges there.
In the accounting firm sector, all work is done by employees. In the law firm and consulting sectors, it’s quite common nowadays to purchase labor resources as subcontracting, in which case the revenue per person is not comparable between companies, unless you can somehow find out the number of subcontractors as well.
Of course, the accounting firm business involves work with a lower value added, but even in larger law firms, the average revenue per person is not over 300k.
Companies also have different ways of reporting part-time employment in their staff numbers, so in many respects, it can be a misleading metric.