I think you are using a massive brush to paint all "programmers" here. There are many types of programmers working on many types of software. Many if us buy dev tools. There are not open source equivalents for everything
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.