I bought an airdam/splitter for my Honda when I first started racing it. The thing was a beautiful piece of engineering and worked great on my car. It was made of quality material so it wasn't cheap.
The first race, a SM missed a shift, spun, I spun avoiding him and went off track. As I drove back on course, I saw my very expensive, well made, now rumpled and crushed air dam lying on the ground.
Since then, I've been making them out of ABS. It's strong, flexible, easy to work with and modify, takes abuse, can be repaired, and looks pretty good...not as good as the metal one, but not bad.
Every once in a while it gets well good and screwed, but I just get out the jig saw and heat gun and make another one.