I don't understand why people think that Mathematica is expensive. Sure, a full commercial license is not cheap, but if you have one of these licenses, you (probably) have a job and the time saved by using Mathematica makes it worth every penny.
I have been using Mathematica since version 1.1, with a commercial license. Granted, the initial cost was about $800 (from MacConnection, if anyone else remembers those times), and the cost for premier service over the years has been much more.
I did a quick price check, and the cost for a student or home-use license is in the neighborhood of $1 (US) a day. Premier service is less than that.
What you are paying for is, essentially, the cost for the R&D and new ideas that are in Mathematica/Wolfram language that are not part of (most) of the 'free' software out there. Wolfram Language is not like languages like c or Fortran, which have a small core, and the user is expected to add (by purchase or writing code) all the extra bits. When I was writing code in c, (before Xcode), what I purchased was the compiler, linker, and IDE (in CodeWarrior or Lightspeed c, for example), not the language itself. With Mathematica, the core language is not really separable from the IDE -- or as it is called, the notebook interface, plus all the access to data (Knowledge Base) and libraries.
In essence, Mathematica gives me a team of collaborators to work on my projects. I have people who can solve PDEs and Machine Learning problems. Do you think that any of the fancy mathematical algorithms in Wolfram Language would even exist if it were not for the efforts of Wolfram Research. (The same can be said I am sure for the nifties in Maple and MatLab.) This type of functionality is not in R or Python. I am happy to pay my license fee so that these people can continue their work.
My opinion is that if you can afford to buy a computer capable of running Mathematica, the incremental cost -- a dollar a day -- to use Mathematica is cheap. Plus, there is always the Raspberry pi and the free versions of Mathematica on-line, although someone is probably paying more for internet access than it would cost to have a desktop version.
I am also aware of the digital divide in the US (and elsewhere) where a substantial percentage of the population cannot afford a computer or internet access. Wolfram Research cannot wave a magic wand and make these problems disappear, and it is my understanding that the Wolfram Foundation is working to reduce the digital divide.
I really do not understand why people think software should be free. Someone has to write it, test it, document it, etc. People working on bits and pieces of a system (linux, for example) in their spare time, are providing a service, but they cannot hold a candle to what a team of professionals who are paid to work on a project can do. Perhaps people think that clothes should be free, or food. Think of what you do: would be ok if the product of your work was free, which would necessarily mean that you would be providing the sweat of your brow for nothing.
Just because the marginal cost of software is (almost) nothing, does not mean that the fixed costs are similarly small. As software become more sophisticated, the fixed costs for any software, let alone anything a complex as Mathematica is huge, and continues to get more expensive.
Anyway, my 2 cents.