Sublime is clearly worth the money, but I've been burned dozens of times by non-open-source software suddenly changing business models or getting bought out and then sundowned. On a longer timescale, it seems that open source is the only way to really keep software alive. I wouldn't be surprised if Emacs (or even Atom) outlived every commercial competitor in the field, including all the ones by the big players. And this is especially important with tools you use for your work!
I wish we had a way of collectively and continuously funding open source software. Developers absolutely need to be paid, but it seems that software is better off when it's free.
(With that said, Sublime is one of the few remaining non-open-source applications that I'm more than happy to buy.)