Yep. Building a working C compiler that compiles Linux is an impossible task for all but the top 1% of developers. And the ones that could do it have better things to do, plus they’d want a lot more than 20K for the trouble.
What's so hard about it? Compiler construction is well researched topic and taught in the universities. I made toy language compiler as a student. May be I'm underestimating this task, but I think that I can build some simple C compiler which will output trivial assembly. Given my salary of $2500, that would probably take me around a year, so that's pretty close LoL.
Interesting, why impossible? We studied compiler construction at uni. I might have to dig out a few books, but I’m confident I could write one. I can’t imagine anyone on my course of 120 nerds being unable to do this.
It's a bit more nuanced. You can build a simple compiler without too many issues. But once you want it to do optimisations, flow control protection, good and fast register allocation, inling, autovectoriasation, etc. that's going to take a multiples of the original time.