I wrote a simple Monte Carlo implementation in Python 3.11 and Rust. Python managed 10 million checks in a certain timeframe, while Rust was could perform 9 billion checks in the same timeframe. That's about a 900x speedup, if I'm not mistaken. I suspect Mojo's advertised speedup is through the same process, except on benchmarks that are not dominated by syscalls (RNG calls in this instance).

The one difference was the Rust one used a parallel iterator (rayon + one liner change), whereas I have found Python to be more pain than it's worth, for most usecases.