Read my post again: revenue / employee, not salary / revenue.
> One can read all sorts of user-level script code, but no source code at all.
What? Probably half of the Wolfram Language is written in the Wolfram Language. How is top-level code not source code?
> it explains why Mathematica cannot be used in serious mathematical work, work meant for technical and scientific publication and peer review.
You keep saying that... I think the truth is more subtle. A tool like Mathematica might play a crucial role in some result, but the proof or result itself doesn't a priori need to rest on any black box software at all to be reproducible.
A nice family of examples would be the class of NP problems, for which the discovery might have been difficult, and achieved via proprietary tools, but the verification is possible via open-source tools or with direct human insight.
And that's not even considering physics, biochemistry, engineering, and astronomy, where many of the tools you use will always be expensive and built by industry, and have no impact on peer review. Especially if they are a means to visualizing data to generate hypotheses, or processing or wrangling data into a tractable form.