A little common sense here. The Force and Hyper series of engines are made for the RTR line of vehicles. The maybe cost the manufacturer of the car 30-40 bucks. When you buy the entire vehicle, you may be paying the price point of 2-3 times that, as well as buying a replacement of the same type. These engines are made to very raw specs as well as using inferior materials. The process is the same as the top of the line engines but not as in depth to keep the cost down. Unfortunetly, its all about the all mighty dollar. I had a Force .28 that lasted 3 1/2 gallons until it became a spectacular fire ball down the back stretch. It came from an RTR and I bought it from the guy who already had an engine for $50 just as a back-up. You cant expect a $100 engine to perform, last and act like a $300 one. You get what you pay for.
Like you said, the Nova and Reedy are just fine. Hence the higher price tag. More design and manufacturing work go into those motors to get them to perform well.
At the end of the day, you got to ask yourself something....
Speed cost money... how fast do you want to go.