It all boils down to supply and demand and the value that each job brings to the company.

In my company the technical specialists earn more than the managers. I think it is mainly because of their technical skills which are acquired through years of specialized training and on the job experience, while the managers are more generalist and thus easier to recruit. Of course good managers are highly sought and command good salaries too.

The disadvantage of being a technical specialist is that mobility is limited because of the narrow field, while it is way easier for a manager to hop to another company.