Hi,
The most expensive things in real time engines are rendering the meshes ( texture, materials, etc etc). Physics also can be a killer. So don't worry too much about using animation curve, Script in general is rarely not the bottle neck of an application.
Having said that, there are few known things to be avoided with scripting:
-- don't find gameObjects in the game loop. The game loop is code that is performed every frame or more than one time per frame. Finding gameObject takes time, so cache or reference your gameObjects in variable and use the variable.
-- adding components and removing components also can create hickups.
Most experienced developer on their talk tell us that optimization should be done after you have your game working. So make your game, make it work, then see how it performs, you can always improve then. This is better then trying to find the optimal way of doing something that you don't even know the full implication in your game... a mistake I did many times... the code ended up in the bin ( but it was very efficient.... conclusion: waisted my time...)
Also, Unity has a profiler window where you can really see where is the cost of things. So run your game with the profiler on, and you'll see where you stand between mesh, physics and scripts.
Bye,
Jean