I get reusable vinyl decals from izoom (izoomgraphics.com). Numbers + class letters for my car = $45 for the larger 10" color numbers (8" black or white a little cheaper). I used them for 7 events, so less than $7 per event! Compared with other stuff (tires, brakes, fuel, hotels, etc.) this represents less than 1% of my costs to run the car.
