Say you want a car. You may want to go to the dealership and just buy one (Toyota's automated process, thus lowering marginal cost). However, maybe you're the hotrod type and would rather build it and customize it yourself. You pay for someone to help you build it and troubleshoot any mistakes you make along the way. Sure, it took longer to build, and was probably more expensive, but it's exactly want you wanted. I think that's where the value of opensource/support lies.
Commercial open source companies (at least Redhat) use subscription models for their support (in addition to consulting, professional QA, etc) so I don't think they would consider troubleshooting software money earned. In fact, I think this gives them a greater incentive to maintain the quality of their software so they get less support tickets and scale to have more subscription fees per support person. I guess you can say that RedHat, through their support, sells the peace of mind of having that support person if you want to go the open source route.