Maybe?

But that assumes there is a ready supply of people that can fix a certain part, and want to take contracting work. For example, let's say I have an ATI XYZ in my laptop. It has a driver bug and won't work. ATI driver is open source. Who do I hire to fix it?

Except that's not quite true for ordinary proprietary software - there are a number of people who make a living supporting Windows or Active Directory or Exchange or whatever who don't work for Microsoft. There is a difference of degree, in that third parties who support open-source code (e.g. Oracle supporting RHEL) have access to the source, and third parties who support proprietary code usually don't (although it's possible to get a MS read-only source license!) and only have access to compiled binaries. But that's not a huge difference. There are people who are very good at tracing and disassembling compiled binaries, or simply at understanding how the system works even in the absence of code, and they have thriving businesses. Sysinternals, for instance, was a separate business acquired by Microsoft.

(Note that I am carefully using the phrase "open source," not "free software". Part of the free software ethos is that you can realistically modify your code as needed. I do happen to think that the current free software movement isn't very good at delivering on this promise.)