10GB of build artifacts for the debug target.
With that said, there are plenty of small game engines out there, but couple Rust's somewhat slow compile times with the ecosystems preferences for "many crates" over "one big crate", and yeah, even medium-scale game engines like Bevy take a bunch of time and space to compile. But it is a whole game engine after all, maybe not representative of general development in the community.
There's no way the average C++ app uses 250 packages though. It's usually more like 5. C++ packaging is a huge pain so people tend to use them only when absolutely necessary, and you get huge libraries like Boost primarily because of the packaging difficulty.
I would say Python varies but 150 sounds high. Something more like 50-100 is typical in my experience.