Apart from certain government agencies and PSUs, the salary structure in the private sector is generally market-driven, based on negotiation, or may have some sort of pay bands or pay grades in a few cases. The example you have cited is fairly common. To answer you precisely: there is no common salary slab between departments/functional areas, and even within departments.
What it means is that there is no parity among departments and even within a particular department. For example, in the Finance & Accounts department, two executives in the same rank/designation, such as Assistant Managers, may be drawing different salaries. Such differences are more obvious when you study the salaries in Marketing or Operations departments, which are considered very vital for the organization.
Compensation and Benefits Management
Compensation and Benefits Management, an offshoot of HRM, is a very specialized and broad subject. I hope I have been able to answer your query to a satisfactory extent or whet your appetite for more information.
Warm regards.