You can still 'pay' for free open source software, many projects accept donations.
You can also donate your time by contributing to projects.
You can always help pay to keep an open source project running. The same thing is a lot more difficult with closed source software once its been abandoned.
It's not that we don't want to pay for software, and I don't think that's what OP meant when he used the word "nonfree". It's just that we need the four freedoms in case the software takes a sudden turn in a direction we don't like.
Now you're going to ask: How is it possible to support the four freedoms and still charge for the software?
And my answer is: I have no idea, and I don't care. It's not my job to come up with a business model for you, I'm just stating my requirements.
I don't think it's that big of a deal for a text editor, though.
One thing is if you're a designer and all your files are PSDs and you're locked in with Photoshop, but if Sublime Text dies you still have lots of other editors that will open your plain text files: Atom, Eclipse, etc.
Usually paying for something helps it not to die, like limetext, for example.
For my work, I'd rather pay for something I rely on to increase the likelihood of it staying alive and keeping up with the work I need to do.