Recently, I have sold and marketed services in a company dedicated to a fully open source software distribution, Open Technology Real Services (OTRS). The services we sold helped organizations deploy the software more efficiently and more expertly, and the company provided ongoing support and maintenance services in an annual subscription.
With a pure open source model, anyone can have access to all of the current packages in a release at no cost, so price is never a factor when it comes to the software decision. I had to count on the engineering team to listen to the community and to our paying customers for guidance and direction, trusting they would engineer the best new features into the product. But if we only engineered good software and sold nothing, we would not have a sustainable business.