It's really not that simple, because payroll processing isn't just the part where an amount of money is sent to a bank account. It's tied up in a lot of complexities like accrued time off, time off used during the pay period, which pool of time it came from, potential for comp time or overtime, etc. That's not even getting into benefits like payroll deductions for health insurance, the choices of different insurance types, performance bonuses, annual cost of living increases... There are a ton of variables involved, this doesn't scratch the surface.