Others have mentioned existing efforts to form reproducible results. So, this might be irrelevant now; but I’m fairly sure if the mindset was “open source compilers are always better than extremely expensive ones”, the expensive ones wouldn’t have a reason to exist.

Actually their reason to exist is that some software and hardware platforms don't have a real open source alternative.

I have a friend who works with some of these compilers, and also with low level assembly language and stuff. He tells me most of the closed source compilers he works with are way behind the open source ones including Microsoft's compiler. I've seen some evidence of this myself too. The reason people use the Microsoft one is because it integrates better with the Windows APIs and Visual Studio, or just because they don't know better. I believe Microsoft even have an initiative to integrate LLVM into Visual Studio because they know how bad their compiler is in comparison. Since it's by a large company specialising in systems software theirs is probably one of the better examples.

In the Apple ecosystem they use LLVM for C and C++. The only stable Rust compiler afaik is LLVM based, though they are working on their own alternative which will also be open source.