The salary of top management stuff and menial workers in big companies differ significantly. This difference allows motivate ordinary workers for further development. Moreover, high salary appeals gifted managers and prevents them to be reemployed by rival companies. So to my mind it solution is absolutely justified.
First of all, the talented manager is a major asset for any company, as he determines a success and prosperity. For example efficient management's decision on proper time for advert or modernization or launching new project will lead company to complete success or total failure in fierce global market competition. These decisions are utmost important because of their scale, as they applied the big company. Furthermore, as a major factor for success, top manager stuff could be reemployed by business rival. Therefore labor market is overcrowded; the gifted managers which could understand and manage people in business setting are always at scarce. Hence, high salary is a powerful mean to retain the talent.
Fairly high salary serves as proper motivation for further development. For example, menial workers who didn't get a necessary knowledge or skills for various reasons as a poverty or unwillingness will eager to learn in pursue for promoted position. Consequently, it could turn out that not all of them will meet the condition, though some talents would be discovered.
The leaders of big companies are getting salary that in many times more than salary of ordinary workers. I think this reasonable as it is the main engine for further personal development of prospective candidates and insurance for the company of the long and prosperous collaboration.