At least over here in Europe you can still get the smaller models (e.g. Carrera Go!) for little money. They're really just cheap plastic toys, though.
The "proper" Carrera 1:24 scale models can be connected to a computer and you can tweak acceleration, brakes, (virtual) fuel intake and other settings. You can have simulated pit stops & lane changes, and it keeps track of personal & track records among other things.
It _is_ insanely fun, just wait for the right deal! 😊