I think even more important question is "what essential dev tools you've purchased that had some sort of open source equivalent".
As for me, last thing I remember – I've purchased http://theolabrothers.com/sip/ when is wasn't free. And it is just a simple tool I don't require at all (any image editor can be used instead), it is just much more convenient than any other alternative.
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What are some essential dev tools you've purchased that lacked any sort of open source equivalent?
I think even more important question is "what essential dev tools you've purchased that had some sort of open source equivalent".
As for me, last thing I remember – I've purchased http://theolabrothers.com/sip/ when is wasn't free. And it is just a simple tool I don't require at all (any image editor can be used instead), it is just much more convenient than any other alternative.