10x slower seems unlikely - if in python you’re using the same rust serde library for your json parsing or whatever, E.g. you “poetry add orjson” to pull rusts serde lib into your python project, then the actual serde operations themselves will be native rust speed.

The problem is IMHO less the increased runtime cost, but that it also tends to get less reliable, robust, harder to get actual right (instead of just somehow working) etc.