Open source software is well known for being "free" as in free beer. Many people start using open source software because it's cheap. And while open source software has a lower "total cost of ownership" than proprietary software, i.e. it's cheaper to use open source software than proprietary software, that's only partially because it's free upfront.
As anyone who uses open source software can tell you, open source software is only free initially. Then, like all software it costs to maintain it, trouble shoot it, upgrade it, etc. Only a few like this open source cheapskate that Matt Asay blogs about expect it to come with free customization and support. With open source software you still have to pay or spend time on: