# Difference between size of market and marginal cost

My question is based on a Cournot competition model with linear demand, $$p=a-bQ$$, but can also be applied to most competition models.

I wanted to know whether there is some special interpretation of the difference between the size of the market, $$a$$, and the marginal cost of the firms $$c$$. I understand that you have to assume that $$a>c$$, otherwise firms won't have an incentive to operate at all. But is there some other interpretation of $$a-c$$? Perhaps something to do with market power?

Thank you and sorry for the noob question.