Why are some car replacement parts so damn expensive? According to the experts, it comes down to performance. Sure, generic brake discs could fit your Mercedes-Benz CLA, but you'll burn through them in no time, because they aren't built perfectly for it. "Generally, people will cut corners," says Santo Spadaro, proprietor of Dominick European Car Repair in Westchester County, New York, and that will cost them in the long run. Derivative brake discs or drums, for example, cost as little as $20 off-the-rack at an auto parts store, while getting it direct from the manufacturer can cost seven or eight times the price. But once they're installed? It's only a matter of time until you replace them again. So, you bought a vintage European treasure. Now you're going to need to maintain it — and that isn't going to be cheap.