Sourcefire SELLS the product, flat out. If anything, they're more of a 'freemium' offering where the free product is a GPL product, and the 'premium' is a faster release cycle for patches / upgrades / definitions.
Covalent sells Apache. I've dealt with Covalent products at a number of federal installations, and I've never once seen a Covalent services rep. If their aim is to sell services, they're not doing a good job.
There are a cornucopia of other examples as well, but these are the three most fitting the description you claim doesn't exist. They do in fact exist, and are making money selling GPL software. That they also have services divisions has nothing to do with whether or not they're making money from selling software.