Having worked in private industry for 20 some years I am familiar with the use of contactors to augment the in house staff.
So the first thing is to define what you mean by "Government Contracting" and "Corporate".
If this is purely a private sector job, not with a government contractor (support contractor) than to me corporate job implies "in house staff", you are an employee of that company.
In this scenario a contractor would be used for a specified period of time to augment the in house staff. In this situation the employee would probably receive a lower salary but would also receive benefits, leave, insurance etc - that would be either partially or fully company paid. The contractor would be given a higher "salary" because the job is short term (specified number of months, and the company contracting out for services doesn't have to pay for benefits and other employee related services (taxes).
If you are talking about a firm that provides contract services to the government and the "corporate" probably means you are not being paid with direct funds.
You are on staff and paid out of overhead. The pay for the employees that are billed to the government is going to depend on what the contact will allow and what the customer wants to pay for that employee. The people who are being billed direct are the ones that pay for the "corporate" positions. The money they pull in includes the overhead to pay for the staff jobs. The salary for the in house people has to be kept low as it affects the "cost" of the people they use to bid for the work. The lower the better.