You're confusing the tradeoff. The tradeoff is not about money; libre software can be sold as well.

The point in question is whether you should have to (or even be able to) sacrifice your intrinsic rights, such as your right to modify your own property for your own purposes.

Whether or not you paid money for it is irrelevant to that aforementioned right.

One example of this beneficial effect is the appearance of the netbook. Only after netbooks running Linux gained significant market share did Microsoft consent to license Windows to netbook makers at a price that made any sort of sense given the low retail price of the netbook. If Linux has not been an option for the early netbook makers, it is likely that hardware makers would never have been able to persuade Microsoft or Apple to consent to allow the product category to be created in the first place.

An argument can also be made that without at least a small fraction of computer users running Linux on their desktops, Linux would not have been able to capture the hearts and minds of corporate decision-makers with the result that Linux use on corporate servers might not have exploded the way it did in the late 1990s and first years of the 2000s. Certainly, Linux activists claiming to understand the thinking processes of corporate execs were saying at the time (late 1990s) that Linux needs desktop users in order to be taken seriously by mostly-Windows-desktop-using corporate execs and IT managers.

I will concede that at least some people (particularly, perfectionistic people like me or people who are easily annoyed) by will waste less time learning how to admin their machine if they run OS X than if they run Linux. And I will concede that the time and effort of these people would probably result in more social good if it were spent earning money and donating that money to a philanthropy than if it were spend learning how to adminning a Linux box. But that does not detract from the fact that if all you know about a person is that they run Linux, they're doing more "expected good" (a statistical term) for the world than someone who all you know about them is that they are a computer user or an OS X user.

For instance, I can buy a hammer because it will make it much easier to drive nails than without one, but the handle is too long. So I can saw the end off to suit my purposes. You can't with proprietary software.

Also, don't make the mistake that free == libre. It's the fact that you're paying for proprietary software, not that your paying for it.