In 1993, you were almost certainly going to have to pay money to write software on or for Mac OS. In 2013, you most certainly do not have to pay money on or for Mac OS X.
>In 2013, you most certainly do not have to pay money on or for Mac OS X.
You have to join the Apple Developer Program, which costs $99/year, in order to distribute software that will run on OS X with default Gatekeeper settings. The registration for that program is currently down.
Which is Apple's prerogative. I can't speak for the average user, but given the number of times that, say, Transmission has been downloaded solely through MacUpdate and CNET (1.5mm), it seems pretty clear that many users know how to turn Gatekeeper off.
Xcode is free-as-in-beer. You can install this if you want to avoid Apple's tooling: https://github.com/kennethreitz/osx-gcc-installer
Ruby, Python, Perl and other interpreters come standard with OS X. As does a terminal. Things are better, not worse.