The numerics in Matlab are far better than pretty much any developer can produce in production. This is why Matlab is used in production - it's vastly more reliable than people rebuilding the things it is good at by hand for bespoke solutions.
Most industry Matlab I've seen is similar to numpy code, heavily vectorized to make it work fast, somewhat inscrutable for everything that's not linear algebra, and a lot of assumptions about perfect floating point precision. Couple that with a unit-testing unfriendly culture and you have a code disaster. Especially on 170k lines.
Most industry C/C++/Java/Python/XXX code I have seen in production is a numerical disaster. I've been working in all these codebases for decades.
There's nothing you just wrote that is any better in any other language, except that Matlab provides a huge suite of state of the art numeric routines that almost no everyday developer could come close to making as solid.
Writing a nicely illustrated manual on brain surgery with nice fonts and proper grammar based on 11th century medicine is of little use for doing actual brain surgery.
Writing clean code based on bad numerics is also of little use for producing good results. Especially if you then have to defend that codebase in court.
Bad developers will make bad decisions in any language. At least using solid numerics underlying the code provides a huge benefit to building the entire codebase instead of on crap numerics. Every nice clean codebase I have been part of has still had crap numerics. Good numerics is nearly completely orthogonal to clean code, and it's a highly technical skill set that almost no developer has even an inkling of how to do well, no matter how pretty their formatting and documentation. I have never in 30+ years of working on highly technical teams worked with someone who really gets the nuances and details of how to do solid numerical code. I routinely get codebases and developers that do the absolute worst things numerically. I have only really good people in conferences on such topics, or online from similar filtering. These people are extremely rare in software development, to the point I don't think I've ever met on on an actual project (and the numerics when needed have always fallen to me, and I've often been selected for technical projects because such people are terribly hard to find when needed).
Not necessarily. I'd happily do it for a reasonable hourly rate + transportation. It would end up costing not more than a few thousand dollars, which is very reasonable given our legal system.
Hell, if it seemed outrageous enough I'd probably do it for transportation costs alone.
It might not be as much as you think. I know professionals who’ve been paid a few hundred dollars to be an expert witness more than once, but usually in medicine. It’s easy money for someone if a lawyer often does certain cases that require an expert witness.