These are not contradictory. People still buy services. Also, you don't have to charge users directly. Three simple examples:

- firefox - open, free, gets money from google

- openmoko - open mobile, you can even download their pcb design and CAD files, but they do sell the product

- specialised apps - company I work for releases some code as open-source, but that doesn't mean that our users have resources to provide the same service themselves, so we don't lose anything