It's not very arbitrary. The reasoning (in one of the upstream posts) is that Python is one of the world's most used programming languages. It definitely makes sense for large multi-billion corporations which are the users of this language to help finance it.

Your point would make more sense if the claim was that a significant portion of the corporation's profits should go towards financing Python. Then I would agree that "there are so many better things to finance than Python". But if we're discussing a salary or two in the context of corporations that employ hundreds of thousands of people, then your argument makes much less sense in the current context. There are very few things that would have better marginal utility then paying for the (effectively) third full-time Python developer.