Qualifying Ferrocene was way, way, way less expensive than that, and they've already had multiple versions of Rust qualified. The incremental qualifications are even easier and cheaper than the initial one is.
I'd believe it, but from talking about this with the Ferrocene folks, there's just structural issues why it was much easier to qualify rustc than it has been to qualify C compilers. This is how they're able to offer the product at a significantly lower price point, and how they've been able to fairly regularly re-qualify new versions quickly.
