You are right about the added cost, but having the fuel pass through the injector at a higher pressure atomizes the fuel more completely which means more of the fuel is being spent during combustion and less is going out the exhaust. same thing for having the fuel delivered directly into the chamber instead of going through the intake and mixing with the air. So in therory, you should see better gas milage, more power, and less emissions, but all of that comes at a cost.