Provocative tagline. It's worth noting that most open source users do so not to avoid paying, but for more idealistic and teleological reasons.
I work on embedded systems in renewable energy manufacturing. I can't imagine what it would be like trying to deploy some of our stuff if we had to worry about database licenses, subscriptions, or any of that stuff. Negotiating licenses with several vendors for each project would be horrendous.
OSI-licensed software isn't "usually" anything, it's always completely free, both beer and speech.
(The challenge is how to keep charging for it since anyone you give it to can also sell it or give it away.)
The biggest advantage is that once your lawyers approve the (L/)GPL, Apache and BSD licenses for use you get access to a vast range of stuff with no more legal work to do. Vendors aren't organized enough to pool a small set of standard licenses.
Compare that to major enterprise software where everytime you need to install it on a different machine, move it from one machine to another, etc can require careful licensing management. At one corporation I worked for, licensing tracking and management was a major portion of the work of one fairly senior person.
Python is, in my own personal opinion, the best language for much of what I do. I prefer it to say C# with Visual Studio, for most projects, and I have a fully licensed and paid for version of Visual Studio (I do use C# for a few things where it works well, especially in conjunction with SQL Server). I prefer FireFox to every other browser on the market. I do not do heavy image manipulation, but for the little I do I think GIMP works better than Photoshop.
Of course, I also use proprietary software. I do use C# for some projects. I prefer SQL Server to all other RDBMS, including MySQL. And I have yet to see top rate video games from the Open Source community.