Typically, the main factor that raises the price in a luxury or sports/performance vehicle is the amount of extra research and testing required to make sure the vehicle meets higher standards with the latest styles and features.
Sports Car Engines
A lot of financial focus goes into the design of the engine with sports car design, due to its importance in that type of vehicle. An engine with more horsepower needs to be stronger to withstand that power. While it is fairly easy to just make the engine thicker, this would as a lot of weight, which would have negative effects on other performance factors, such as handling.
Durable Drivetrains
A powerful engine produces a lot of torque, and enough torque can break components trying to get that power to the wheels, so a robust drivetrain is needed to handle the more powerful engine.