Any organization that reaches a certain size will encounter things like this. The larger an organization gets, the more the productivity level tends to regress towards the mean. So, people with higher productivity will likely feel unfulfilled and people at the lower end will still feel inundated. It is both a mechanism of success and a detriment to such organizations. Successful because it standardizes things, ensuring more consistent quality and productivity overall - the end goal, after all, is to eliminate uncertainty as much as possible in daily operations. Detriment because, pertaining to the the consistency of quality and productivity, it tends to regress at a lower level.
The salaries tend to be higher simply because these large organizations are typically much better capitalized, not necessarily because the people that work there are that much better than everyone else. This is why a lot of high performers tend to strike off on their own at some point in their careers - dissatisfaction with mediocrity. But then their own companies, if successful, grow to a level where, once more, productivity and quality regresses towards the mean and they find themselves in a self-created bureaucracy as the organization matures.
The salaries tend to be higher simply because these large organizations are typically much better capitalized, not necessarily because the people that work there are that much better than everyone else. This is why a lot of high performers tend to strike off on their own at some point in their careers - dissatisfaction with mediocrity. But then their own companies, if successful, grow to a level where, once more, productivity and quality regresses towards the mean and they find themselves in a self-created bureaucracy as the organization matures.